From what I understand, the Jam goal is to create games for novice players. That's why each game must contain a tutorial - introduction with the game mechanics etc. It must only be suitable for children (no offensive content).
As of banner art-work it's a fun, cartoon-style graphics, I like it very much. It suits very well with the optional Theme (time-travel). It's a style that was used in previous edition and in my opinion it's targetted to wide audience. It just makes sure that the games must be a bit not serious and don't contain very hard puzzles.