OK, I have been following the movie since last year when concepts of the movie first leaked out. I had friends that saw a storyboard sequence of a scene at last year's D23 convention (which they loved and can't wait for the movie). I even saw the mock arcade cabinet Disney had for the game, and I found out about these cameos from this article.
If Bowser and the rest of the characters will look like their actual selves (as in, they will look like the actual characters and are not fake interpretations of it) I am completely sold on this movie. Yes, I was already interested in the movie based on its concept, but this has not sold me.
The same D23 article also has artwork of other worlds, and the Halo-Space Marine world looks great, especially in how they captured the sci fi aspects of it.