Bigger.
Clean up some of the angles on the text, they don't match the ones of the box.
And although you said it's pretty much set, changing the 'Mechs wouldn't be a bad thing. It's pretty difficult to distinguish certain 'mechs, like the
Templar or the
Deimos (I think that's what that is?). They don't blend terribly well with the box either.
Then, like you said, the background could take a change. And maybe spruce up the text a bit.
Oh, also, it'd be "So you want to pilot
an Atlas."

Pretty cool idea. I'd like to see how it turns out.