Oh! I'm acquainted with a couple of them under another name, through forums. You might try Eatpoo.com's forums, though they're a pretty tough group, or else ConceptArt.org. I get links to most of them from friends, though--I was introduced to the art of Matthew Woodson, Paul Pope, and James Jean by one friend, for example. I'm also subscribed to Drawn.ca's RSS feed, which tends towards cartoony stuff (actually not my preference, despite my own SGA fanart--for some weird reason, they almost never hit my preferences for art) but is still a great resource.

And yeah, Nivbed's fantastic and everyone adores him. ♥ Did you see this one (http://www.nivbed.com/desire.htm)? That's my favorite.

(And woah, Lawrence Alma Tadema's marble is amazing.)