Let's be honest, nobody really likes ads. We might admire the artistry of a few, and there are things we do want to know about, but at best, advertising tends to be regarded as a necessary evil.
So, having said that, why stick ads on Weasyl? Because they are a very effective way to let people know you exist, and they would be an additional source of revenue to help keep Weasyl going. Obviously, you would need some guidelines about content, and you'd want to use the same rating system as other content on the site, but if you could make that would, it would seem to be a very useful addition to the site.