I'm looking for anyone who knows any websites/blogs/users who take request for pictures. For example, id want to see a certain character that didn't have much art anywhere. Where would I look?

Deviantart.com is one of the most popular and easy to use. Also has a plenty of people who does requests, putting an icon "requests are open" in their profiles etc.

Hentai Foundry. Plenty of smut artists to shop around.