Your current repertoire does sound a bit one-note (no pun intended); I don't mean to criticise (I went through a phase lasting almost a year when I only played pieces by Chopin despite my teacher's best efforts to persuade me otherwise), but it does seem to hint that a bit of variety might be helpful. Unfortunately I can sympathise with the problems of finding participants for chamber music (I've had to advertise quite aggressively to find anyone, and the only reason I received any replies was because I'm a graduate student and hence have a whole university to which to advertise), but it may still be worth a look, at least.
And branching away from early Romantic would definitely be a good idea - perhaps some Impressionist? I admit I was very relucant to go anywhere near Debussy during my Chopin-centric phase but when I finally stopped resisting my various teachers' suggestions that I give him a try, I knew they'd been right and I'd been wrong. It sounds as though you could quite handily learn the Arabesques, the Suite bergamasque, or some of the Images. Or you could try looking through some Ravel, or Faure - Faure seems to be unjustly neglected next to the other two, some of the Barcarolles and Nocturnes are particularly charming. If you'd prefer something with a bit of fire, perhaps some Prokofiev, or Rachmaninov? (I can't readily suggest specific pieces by those two but there are plenty of people on these boards who can, so perhaps one of them will speak up.)
If you go back in time instead and look at some Bach, don't just look at the Inventions, Sinfonias, and Well-Tempered Clavier - try the English and French Suites, or the Partitas, or the Toccatas. Or perhaps some sonatas by Scarlatti or Soler? They're well suited to the piano (indeed, some of them arguably sound better on the piano than the harpsichord), and the choices are almost endless.
I'm no expert on modern or post-modern music, as it's not my cup of tea for the most part, but perhaps it might be what your repertoire needs at the moment? Might be worth a look (as several respondents to this thread have already suggested).
As pianote says, variety is key to remaining interested - and, arguably, interesting - as a pianist.