I would definitely recommend you play some of Nikolai Medtner's Fairy Tales, especially op. 20 no.1
They are pretty difficult, but definitely worth the time!
I second the Medtner. He is not played super often but extremely rewarding. Other Suggestions from him would include his Op 51 set of fairy tails or his Sonata “elegy” op 11 no 2.
If you want to do some more Chopin you could do his 2nd or 3rd ballade or possibly one of his etudes.
If you like Scriabin you could look at op 38 or one of his etudes from op 8 (except for maybe no.10

)
You could maybe do one of his sonatas 2, 4, or 9 though those might be a bit of a stretch and would take a lot of effort to bring to a high level
Have you considered a Beethoven or Schubert sonata?
Maybe one of Liszt’s transcendental etudes (I’d stay away from 4, 5, 12 and maybe 10 for now)
Have you ever looked at the Spanish repertoire? The Iberia suite by Albeniz is awesome (and difficult

) for now I’d stay away from Fete Dieu a Seville, Triena, Lavapies, and maybe Eritaña for all four are technical nightmares
That’s all I can think of so far. On top of this it may be smart to maybe choose a Bach P&F from the well-tempered clavier or one of his French or English suites for I believe it’s always good to be studying some Bach
