It will be interesting to see what size and quality of images end up becoming the popular choices in the database.
I hope people don't upload 1500x1500 and larger images just because larger is better. In cover art scans, larger is not always better. 1500x1500 and larger images end up with visible dot patterns due to the printing process. They become
moiré monsters. Large images need to be scanned using a
descreening filter and then cleaned up in an editing program. Then the images need to be shrunk down to 600x600 or 500x500, cleaned up in an editing program some more, and then finally they're ready for cover art. I hope I don't end up seeing lots of big 1500x1500 images in the database because those images are unfinished and unready and need lots of editing before they're ready for proper cover art.
I've standardized on 500x500 for myself. If it's an image that I'm going to upload to AlbumArtExchange I'll do it as 600x600, but I'll usually also make a 500x500 version for myself.
Most of the images that are in my library are either scanned and edited by myself, gotten from AlbumArtExchange, gotten from Amazon, or gotten from Buy.com. Those are the images that I end up uploading to the JRiver database. Some of my 500x500 or 600x600 images are over 200K. I try to avoid over-compression and would rather have them big than have JPG artifacts. I wonder if people are going to decide that 200K+ is too big and my images will get bumped off the JRiver server? I wouldn't be surprised if that happens.
I've put some of my cover art on Amazon as well. Amazon recompresses JPG images to heck, but you can also upload PNG images to Amazon. Amazon doesn't butcher PNG images when recompressing them. So if I have an image that looks horrible at a low JPG level I'll upload it as a PNG.