1. I am the boss.
2. The boss is always right.
3. If the boss is wrong, see rule number 2.
Seriously, after looking into what all it takes to make a theme, I think that it might be too much to ask for a contest.
We always setup our standard web site for 800 x 600 pixels so I would suggest that we use this size, as it is the most common screen resolution according to all the web stats that I see.
I also think we should put a limit on the file size like 500 kb max, to accommodate the dial-up members.