I would definitely recommend starting with “realistic” characters. Pixel art is just an abstraction of realism, just as all the other styles. Consider that there are at least these styles you could render your characters in… I supposed pixel art could be added:
Expressionism (and Abstract Expressionism)
Arts & Crafts
Die Brucke / Dada
Constructivism (Russian Populist)
Cubism (probably the closest to “pixel art”)
Minimalism (and Color Field)
Only some of these styles lend themselves to game productions and some don’t… but innovation and creativity come from doing the unexpected.