the op.45 etudes of Scriabin, not just no.5 but all of them, they're 8 if I remember correctly, most of them deal with polyrhythm and left hand of course

. The Chopin preludes are a good choice too, just like le poet said. You could try also some of the later post "mystic chord" era preludes of Scriabin, or his op.63 etudes, they're just 3, each dealing with intervals, 9ths, 7ths and 5ths.
Prokofiev's visions fugitive op.22, 20 miniatures with a wide range in mood and are a great example of Prokofiev's style, Charles Rosen considered them Prokofiev's masterpiece. Together they don't last more than 40 minutes.
Debussy's Etudes, 1 of the 2 books, or both. Preludes, estampes, etc.
If you want a big challenge you could also try Bartok's 3 etudes op.18.
Ravel's complete Mirroirs.
.... etc.