Seeing the Playtonic logo 'area' in space and the box art with galactic elements in the sky above Capital B makes me think how amazing and magical a galaxy level would be. Maybe the final world -- the last level of Banjo games were always the most magical.
It'd also be cool to find yourself in the logo space area at one point. The elusive area you see every time you turn on the game...
If not a whole level, perhaps the Glacier World could somehow hold a massive secret in the night sky. The Glacier World's sky somewhat resembles the magical logo area and could somehow be connected. Maybe there could be a way (e.g. looking at a Playtonic constellation after 100%ing the game) that transports you into the super secret galactic area of awesomeness.
My imagination is running a bit wild, but I definitely love the space aesthetic seen in the logo startup area and think it could really make a fantastic place to visit. I also think that area could become somewhat of Playtonic's trademark, featuring in all their games etc. (it looks so magical, I think I'd like that).