This is a cross-post of my original decoupage plate picture frame (sort of) since I got a response from someone about making one as a wedding gift. I'm offering up a picture of how my invitation plate worked out that I made for my sister-in-law last month. It's not a great picture, but you get a good idea.
Since I made her invitations for her, I just printed out one of the invites on a regular sheet of computer paper, and trimmed it to fit the middle of the plate. The edge of the plate is pink & gold scrapbook paper I found at the Dollar Tree. The back of the plate is painted pink, and then sealed with Krylon Triple-Thick Glaze (I just love that stuff). All in all, I probably have a dollar invested in the whole thing. It turned out to be a really nice addition to the cake table.