That's probably a good idea -- I hate it when the browser gets super wide because of giant images. My 5 megapixel camera shoots at 2592 x 1944 -- I would never upload a file that big to a forum. I think 1600 x 1200 is very generous. (How does it handle it when the picture has been rotated? Maybe it should simply be 1600 x 1600, to allow for portrait pictures as well as landscape).
Please increase the allowable size for ZIP files to 512,000 bytes as well.
I think it's amazing that PSD files are allowable. Next thing you know, we'll be having our own Photoshop contests. Pretty cool.
Also, is there a per member file attachment limit? I've uploaded 3 or 4 pictures so far, and I now see a little status bar that shows about 1/3 red, 2/3 green. This might be a feature that we disable for RS members -- i.e., members can upload unlimited images.