Hi,
I will introduce some Chopin's rarely played, but actually wonderful pieces technically & musically:
1. Introduction & Rondo (Rondo No. 3 in E-flat Major, Op. 16)
2. Allegro de Concerto in A Major, Op. 46
3. Krakowiak, in F Major, Op. 14 (originally for Piano & Orchestra)
4. Polonaise-Fantaisie in A-flat Major, Op. 61
The 4th one perhaps has been performed quite often, but it's still a niece piece. So you can choose any one of those titles above & start practising. Good luck!
Best regards,
Joseph