I have a nice selection of Dark Heresy and warhammer 40k related artwork. However, I am still lookign for good images of NPCs and also of locations and places that do not involve Space Marines.
My opinion of Space Marines is that if they are seen in my campaign from a distance, not close up.
-Chrysalis
I have a ton of images on my computer, most of them aren't of space marines. You should check out deviantart.com they have a lot of good 40k artwork. I would suggest looking at other sci-fi art as well and some steampunk and fantasy art might also fit.
Here something I made awhile back, http://www.darkreign.org/downloads/30-12-2013/40k-portraits-and-busts-14
I need to update it,