The idea behind this is simple:
Claim a square, and draw an image for it.
However, your image must connect with those around it
at the time it is posted, so if someone uses an animation, you may have to animate yours to get it to line up properly.
Numbering, for convenience, is alphabetic across the top and numeric down the side.
Remember, it must fit at the time that it is posted, so be wary of claiming a square bordering another claimed but unfinished square.
Finally, I will make a local copy of your work, so don't think that you can secretly alter it after. If you do, your square will be rejected and reset.
At any time you may request that any of your own squares are reset and made available.
Edit: since some programmers count from 0, but most non-programmers don't, I'll clearly state that the numbers are 1 to 8, and the letters a to h.
Edit again:
Before anyone has to ask, yes, you can draw more than one square, or even combine a few unclaimed squares into something larger.
However, to prevent malicious space hogging, you will be restricted to four claimed-but-not-posted squares at once, unless you simply ask and people generally don't mind. I guess I can't stop people from claiming more than they should, but I can't stop someone from ignoring your claim and making their own also.
(For reference when none are in the image:
http://img682.imageshack.us/img682/3788/reserved.pnghttp://img706.imageshack.us/img706/5702/badcu.png)