Souvonier (can't spell) contest here. This idea came to me last night when I started my sister's b-day cake because I am making it based on my memory of the nesting dolls she brought home from Russia when she went several years ago for a semester of college there.
I think that would be a cool idea.. but that would just open up to a lot of things. The theme isn't going to be consistent since souvenirs can be anything. So it's basically going to look like just a cake competion with no theme.
Good luck on your cake btw.