Well, if the polonaises are somewhat up in the air, I might suggest the overlooked C minor polonaise (which is...don't quote me...op. 40 no. 1 I believe) and the posthumous F minor polonaise. It seems like both pieces would technically be "below" your level, but that shouldn't exactly be an issue in my book (you and your teacher might think otherwise, of course). You might also look into the mazurkas, which are of course small and idiosyncratic pieces which would be excellent workouts for more off-the-wall kind of things, i.e. out of the mainstream rhythmically and melodically (and they are also short pieces).
And of course there is always Schumann, the miniature master, who happily provides works like Fantasiestuck, Kinderszenen, and Kreisleriania, all of which have some excellent, short, and very worthwhile pieces.