Seems that there aren't that many if any programs for this. Maybe some talented programmer and pixel artist will make one someday, you could have a event where two people from the forums would have to collaborate, not knowing each other's forum names, kind of like the Secret Santa thing I saw on the other forum. There could be a predefined subject, et cetera. I'm certainly not going to try to create a program for networked pixel art real-time collaboration, I don't want to mess with networking code at this time (besides not feeling like taking a bunch of time to do something that I am not that interested in doing).