File size will be easier to find then the dimensions, and file size is more important on how fast a page loads anyway. I see an admincp setting where you can set the max file size in kilobytes and any images larger than that value will be replaced with [url] links instead. If I get fancy maybe I'll put the file-size next to the link. Like....
http://somedomain.com/image.jpg (251 kb)
I will probably play with this but no promises on how soon I can do it- if someone else comes along willing to try it I will gladly defer to them.