Try Quilters Cache and look through the names of all the blocks. None really represent those things but you can find names similar enough to tell them they do. Just put a label on the back with the names of each block.

Here is a link that might be useful: Quilters Cache

Perhaps you can get some ideas from this blog:
http://biblequilts.com/

Here is a link that might be useful: Bible Quilts

What a wonderful gift! I like the idea of using whatever blocks appeal to you and naming them to fit the vows.

I would recommend that you find out if they are speaking traditional vows or if they are writing their own. You may be able to personalize it even more if you know exactly what they are going to say. (Maybe use signature blocks and write the statements with a fabric pen?). Even some very traditional churches allow the bride and groom to write their own these days.

Kate

Here's another spin, get the vows printed and put them in the middle of the quilt and use the sampler quilt squares from Elm Creek to surround it.

I like all your ideas and I may have to use them but in the meantime I'm still looking. Nothing has just jumped right out at me.
Thank You
Sharon