Here are some ideas I came up with, some of them are serious, and some... not so much :D

I also made a quick and dirty Google Docs spreadsheet to put them all in one place, feel free to copy it, put in your ideas and share them with the world, if you so choose :3

I tried to avoid going for the first obvious thing that comes to mind and instead try and come up with something a bit more weird for some of the themes.