I think there'll be a difference if you limit submissions. If you realize, some people submit just too many low quality wallpapers at one go. By limiting the submissions, at least the mods do not have to look through so many submissions. I think by limiting submissions, you'll also limit the number of ripped walls since people who rip walls submit a few at one go.
Another thing is that, not many people read the rules before they start submitting, that's why there are still many submissions that are against the rules. Honestly, I didn't read the rules until I was around level 20? ^_^' Besides, if you want to report all the submissions without proper creditting, I think there would be alot >.<