It's always interesting to look at the workspace and home offices of artists. Here are some that I came across recently:

Just head on down to halowars.com for more concept art, available for download as wallpaper.

Features environment concepts, unit concepts, forerunner structures and ambient life concepts.

Oh, conceptships.blogspot.com has more pictures of Halo Wars concept ships from Ensemble Studios.

What happens when you have a ninja who's a jerk? Just go over to ninjerktsu.blogspot.com to find out.