The company told us, "We have set file limits as a general guideline. An important part of Xbox LIVE Arcade is easy access and keeping file size down is a vital part of that. Equally important is offering titles with superior game play. We weigh both considerations on a case-by-case basis, and will make exceptions when it makes sense to ensure the best customer experience."
Hope you don't mind inferior quality pictures of guys in funny hats, because it seems that's what you're getting.