Blood Angels - BLOOD ANGELS! Angels come from heaven, angles come from geometry class.
Anyway, on to the actual model. I like the idea behind it. You got some nice poses, especially with the Necron swinging his weapon over his head. My favorite part of the diorama is the warrior rising out of the dirt. However, the paint is just sloppy. The metallics look really haphazard and ill-defined, while the red is just too splotchy. The Blood Angel should have his red either built up from Mechrite Red, the foundation color, or it could be based white before getting built up to a nice red.
Your painting definitely needs some work, but it's not bad. The modeling, however, is pretty nice. Keep it up, and watch your angles
Edit: One more thing! Washes would do you good. They give some really nice shading to your models for almost no effort. Pick up some Devlan Mud, Badab black and Baal red and go to town!