Good concept. I'd try to make the composition a little more exciting, maybe make the main subject more agile and the mechs around him taking more punishment. It's pretty bland right now; blasts coming in from left to right, mech floating in one place shooting down, getting the snot pounded out of him.
Also keep your eye on perspective. The barrel of the gun looks like it's pointing away from us, but the but of the gun is doing the same, making it look like it's bent in half.
Just keep at it.