Hey-- It seems like you've already covered all the major periods of music... Baroque, Classical, Romantic, Impressionistic, and 20th Century.
If you're looking for something short, maybe you should take a look at Rachmaninoff Preludes (neo-Romantic) or something by Gershwin.
Also, maybe if you want, you can include a late-classical, early Romantic composer, like Beethoven or Schubert.
Hope that helps!