So, I recently started using Tumblr (link to my tumblr) but I've actually had an account for quite a long time. I didn't really use it, because I didn't know who to follow, but I had a handful of blogs. One of them is called "The Art of Animation," and posts nothing but high-quality concept art and illustrations for works of popular fiction. It's beautiful, inspiring, and it makes for some of my favorite posts scrolling around tumblr. Warning -- some of the art posted is (very artistically) NSFW.
Here's an example: