After LittleBigPlanet was announced, a lot of information was released on the game. In particular, a sketch was released showing many characters, particularly ones that included Mario, and Master Chief.
Creative director Mark Healey states that even though it’s concept art, "…you can customise your character so much that that’s entirely possible." With the use of importing stickers from your hard drive, you can literally paste logos onto the thousands of costumes they have.
If you’ve read our preview on LittleBigPlanet, we include a tidbit on these sketches and how you can play as Mario sackboy quite easily. In addition, not only can you import logo’s, but most likely costumes of sorts as well, though not clearly confirmed.
Source: CVG