Seeing some of these mecha pieces have you ever heard of or played the game "Phantom Crash"?
It is personally one of the best mechas for the xbox and it had an excellent online gameplay (before Halo2). Just though I'd mention it since the scenery and mech designs you draw look very similar too it.
This is exactly the kind of artwork I'm completely jealous of... I envy you, Sir. Quick, dirty, yet endlessly impressive in atmosphere, shapes and execution- and with a style that makes me wish to have one, myself. I love it!