OMG, I'm a designer by trade and all I have to say is your a VERY good friend. The hours of labor, designing, sorting... it's a job!! I don't think many people understand. Why don't you buy a wedding album
http://www.target.com/gp/detail.html/sr=1-10/qid=1187457326/ref=sr_1_10/602-8236899-3423839?ie=UTF8&frombrowse=&asin=B0006B5G7K
(CVS, Target) and have the invitation on the inside cover page. Wrap it, with a designer flair and there's your gift. Or, if your a designer, maybe you can make something for her shower.
For my friends shower I made the wishing well with a hamper (something from Target, Walmart) and wrapped fabric around the edges.
Make a flip book, with images of them together
Or get a clothes line cord with clothes pins and hang kitchens towels, mits form them. (Dollar Store). Nobody will notice the price, you have an advantage, your a designer and can make anything unique. It means more than getting a set of glasses from Crate and Barrel.