I am having a flash back to some wonderful art swaps that I have done with friends.
Some of my favorites were altering vintage cabinet cards!
Here is a link to see what those are and the different ways to alter them.
Mine are the first three pictured, but you can hold your mouse over the image and it will tell you the artist that created it. :)

http://www.art-e-zine.co.uk/cabalt.html