Quatral chords, Qunital chords, extended chords, augmented chords, diminished chords, moving chords arround in non-diatonic patterns, quasi-modal progressions (or just modal), progressions based on scales like Melodic Major, Neopolitan Minor, and Double harmonic, etc. the list just goes on, there are so many cool things you can do with harmony, you just need to get out there are research them!
Analyzing peices with interesting harmony is always a good idea.