Hi there!
I have been handfasted to a wonderful partner for the last 7 years. This year will be our eigth knot tying. (I'm Scottish too and like that part)
I do have some Pagan slants to my beliefs, but what makes any ceremony important and real is your belief in it. It does not have to be any ones formula, or one someone has written down two hundred years ago.
We use two beads that were given to us while traveling during the adventure that brought us together. Each year - May Day for us - we pull out the beads and other special things to us and go camping. We usually do the handfasting over night - set up camp and lay out a workspace. When we are done eating and wandering we use a long silk cord to connect one of our wrists to one of the others with the beads hanging in the middle. We then discuss the good and bad aspects of our last year together and make changes. It is a free and open space where we can completely be honest with one another. When we reach the new terms of our relationship we consummate the deal ;) and go to sleep. In the morning we cut the cord from our wrists and tie the beads tight together. At this point it is ball of shimmery silk with just a couple holes in it.
We have been invited to do the ritual publically at parties by several of our friends, but have decided to keep it private at this point b/c every year we are making changes, sometimes very dramatic. I feel that having an audience may make me not talk about some super private issues that need to come up during a ritual like this.
Good luck and I am looking forward to hearing about your experience! Congratulations on living the dream!

I've officiated at a few alternative weddings...One on a beach in southern california and three more out at burning man.

By officiated I mean that I did the set up and preparation of the ritual space as opposed to actually doing the marriage ceremony.

What I contributed to the ceremony in my set up was as follows:

~1~ I set the four points for the compass and made an altar for each element at that compass point. Each compass point has an element (earth air fire water) associated with it. The altars each encompass some form of that element. A large clear bowl of water as the water altar...Some hanging feathers to represent the wind etc. etc.

here's a photo of the one I did at the beach: people.tribe.net/captainer...f35d61f5e7

In this one it was perfect, as the water element was to the west and thus the ocean... During this ceremony the tide came in Juuust enough to spill into the water altar during the ceremony...it was sweeeet...

~2~ As guests arrived I asked them to divide up according to their astrological sun sign element (giving help to those who did not know)...Thus the guests were arrayed according to a circle that inscribed the four cardinal directions and elements. I invited the guests to consider the aspects of their element and to help hold the intention of that energy during the ceremony. This helps to create a container for the ceremony. I call it The Cathedral of Friends.

These are the Celtic Based Elemental/Directional associations:

North - Earth
South - Fire
West - Water
East - Air.

~3~ Once the circle is set then I wait for the groom and bride to arrive. When they are present I "Cast" the circle by invoking the four elements, each in their turn. In each case I ask the group to turn and face the element in question. Then I invite the spirit of that element to join us and bring presence to our circle. Each element has many natural metaphoric associations which apply toward the idea of partnership (marriage) ... Examples of these are as follows:

North - Earth - The home, Material Possessions, Physical Health of Body, Material Wealth
South - Fire - Passion, Intensity, Romance, Creativity
West - Water - Emotions, Change, Going with the Flow, Cleansing
East - Air. - Thought, Intellect, Spirituality, Communication

Again, it is important to note that you can insert whatever metaphors you wish into this part of the ceremony. The cool aspect of this is that it gets everyone present, including the bride and groom, to focus upon the elements of the partnership that they are committing to upholding with each other. Furthermore The Cathedral of Friends is present to bear witness to these pledges of commitment, a reminder that the community of the couple will take part in keeping them to their promises from this ceremony.

So when I invoke the elements and invite them in it sounds something like:

"If everyone would please face North. We turn now to the North and invite the spirit of the element Earth. We ask that you bless the home of these two. May their hearth always be warm, their board laden with nourishment. Nurture the union of these two, so that their bodies may grow in health together towards fruition. May the roots of their love be deep. May the intentions of this ceremony crystallize into the rock of their partnership. Let their life be wealthy in all ways...."

(A nice pause works great here... to let the intention sink in.. then I finish the elemental invocation with)

"I would now like to ask all the Earth Energy people to make the sound of earth so that these two feel the presence of this spirit and honor it's aspects well... What does the Earth sound like....?"

At this point all the Earth people then come up with an improvised sound that represents the element (which if I may say , kicks ass in any number of ways

~~ it's silly and fun , adding a moment of irreverence to the ceremonial vibe
~~ it's powerful to see people reach into themselves and pull up a sound representing an element
~~ It's really fun to watch the group adjust to itself instantly, making a conglamoration of sound that really sounds like that element
~~ It's a physical representation of something abstract. In my world view, those earthsign people actually channel or "become" the Earth Spirit for that time during the ceremony. (ok ok I admit this works especially well with a bunch of burning man people in the dessert but it will work with any group. Even one that does not put much stock in astrology. Everyone knows what "Earth" or "Fire" is...)

Obviously I go to each direction and do this for each element until the Circle is cast and the Cathedral of Friends is constructed.

At that point I turn the circle over to the person who is going to actually marry the people and they take it from there.

In all the cases of the weddings I have performed at, the couple created their own vows, or at least morphed traditional vows into their own languaging.

I think in the case of creating a ceremony. It is possible to add in other elements to the experience.

~It would be fun for example to hear a few very brief one line testimonials to the people about to join together. IE - A woman steps in to the circle and says " [The Bride] is by far, the kindest person I have ever met" after that another person steps in and says "[The Groom] Gives kick ass back rubs" ... just another way to heighten the sense of the group knowing what two people are coming together. Keeping it to one liners makes it quick. Perhaps three comments for each of the couple could be made. This concept could culminate in a few one liners about the couple themselves: "I've never seen two people who make out as much as Bartholomew and Isadora"

~ I performed two songs for the wedding of two friends of mine. It was a more traditional wedding, with a few hundred guests sitting in rows of chairs. But it was also outside under a huge oak tree and there was a perfect earthen stage. So these two songs were written by me about the couple. In both cases they were also sing-along style songs so the audience could participate. In between the time when the couple said their vows and the time when they said "I DO" myself and another friend performed these two songs. I can't say enough how much that impacted the wedding ceremony. The audience, instead of sitting there in stifled, reverently restrained happyness, was hugely alive and glowing with energy after helping me sing. So if you know of anyone who makes music, having them perform something during your ceremony is a great way to both include the crowd, entertain them, and also, make a musical celebration of your union. (In my case I took the song Aiko Aiko All Day... and turned it into "Jocko...Jocko All Day" (Jocko of course, being the groom in question)... so having the crowd singing along with "HEY NOW- HEY NOW.. Jocko Jocko All Day" was an enlivening way to make a witty commentary on marriage.

~ Also any form of visual performance is cool. I would love to see a firespinning act where the bride and groom stood on either side of the fire so that the crowd would see the fire "weaving" their energy together... So things like that .. such as a dance performance that included the couple.. add to the ceremony by making them less about words and more about visual metaphor... cermonies get pretty "talky" so adding a visual performance helps stimulate the minds of the crowd.. keeping them more deeply engaged

~ During the actual wedding ceremony it would be fun to mix it up a little.. It's usually so staid and formal two people stiffly standing there... I'd like to see a "pre-kiss" where the two get to kiss one last time BEFORE agreeing to marry.. and the crowd gets to see a nice hot kiss to see how the two join together... or how about anything at all that makes the couple move .. like a short dance, mid ceremony.. or having to play patty cake... or hold hands and spin around in a circle three times... or jump up and down a few times....just anything to mix it up and get things moving physically and thus energetically

~ Lastly, this is more for the reception part of things, but having art supplies out so that your guests can make a work of art to help you remember the day might be fun

~Good luck with the planning of your ceremony~