He looks nothing at all like Gurren Lagann.
He looks like Enki
, he even has the Shoulder Rocket Launchers
A White coat and some swords would complete him.
I had considered that, but Enki is very lithe, where Rumble is very bulky. Enki's hips are noticeably wider than his upper torso is; it's shoulders are actually in line with the plates on it's waist. For the sake of mentioning it, Lazengann's silouette is similar to Enki's.
Gurren Lagann (and Tengen Toppa Gurren Lagann), on the other hand, has broad shoulders and large armor plates attached to his shoulder. It's also much bulkier, which Rumble seems to emulate.
I concede that GL doesn't have the back mounted missile launchers, buuut it's worth keeping in mind that the homage here is first and foremost to G1 Rumble, who had back mounted missile launchers. TL;DR
-- Rumble is more bulky, like Gurren Lagann; not lithe like Lazengann and Enki. Plus he's got shoulder armor bits, which seem to emulate the Gurren Brigade logo emblazoned shields on GL's shoulders.
-sigh-, Gurren Lagann was not the first mecha to have a face on its chest. That honor goes to Gaiking. Bonus points go to me since the director of Gurren Lagann made his debut with the new Gaiking anime. The author did GL as an homage to all super robot anime especially Getter Robo.http://www.youtube.com/watch?v=r-nzVrHlkTE
Also, I think it looks more like Gaiking than anything.
I never implied it was the first. I only implied it was the best.
Honestly, I find Gaiking pretty...boring at best. What makes Gurren Lagann mechs so great is how stylized they are.