A group of us have done a compilation book for a friend and her other half who are getting married, each person doing one page and an ATC. Here is my contribution, didn't get a photo of the ATC though.
The background is done with acrylic paints and then overstamped in a gold ink, which you can see if you look closely. The heart is also done in acrylics and stands proud of the background, so the ATC could sit behind it.