Seriously, how many threads in the art forum get "Read the rules." responses?
Adding a paragraph about MS Paint to the Art forum rules ain't gonna fix anything, as mostly only new people that aren't aware of the fact, that they are going to be flamed and most likely banned for posting their stickman, post crappy MS Paint art. People will still say "Sorry, I used MS Paint, but I swear my mom said the drawing was awesome." after a "MS Paint is NOT allowed" disclaimer will appear in the Art Forum rules.
New people that didn't read the rules. Even though lot of stupid MS Paint threads could be deleted without me knowing it, tell me, how many users posted their "art" after they were warned?
And while MS Paint spam won't be stopped, awesome artists like Ngmastah, Raguel won't be able to post their work made in the underestimated, yet original program of MS Paint.
Or, like Razac said, get an IQ 501 artifical intelligence bot that will consider all of the drawings uploaded crappy.