If you haven't checked it out I can't recommend this website enough (just Google it - it's very popular). Lots of science fiction, horro and fantasy art on there with a helpful search box. Artists from all over the world showcase their work there. I use art from there on my blog all the time - but reserve a section on the blog for displaying the pieces I use in their uncropped entirity and acknowledge the artist and their work. Highly recommended if you are searching for a specific kind of picture. Someone is bound to have painted / digitaly rendered it on DeviantArt.