Not really sure on what type of competition pieces you expect, could you be more specific?
[Opus] clavicemballisticum....may be longer than 12 minutes...
Why not just go for two flashy contrasting pieces? e.g Liszt's Spanish Rhapsody + Bartok's Allegro Barbaro?
My teacher want to start learn Chopin Prelude 24 d minor, but I think that it is so hard for me.