Require some minimum resolution for images so we won't have all that pictures too small
Added on Aug 15 14:16
Its quick and easy to upscale images. Given the number of upscales on Google Images used to get page hits, I doubt this requirement would do much good. And sometimes there are no high-res versions of images.
A minimum resolution? You must be out out of your fucking mind. There's not even a maximum on this site! You have all the freedom you could possibly dream of when it comes to uploading on this site, and you rather restrict yourself?