Mussorgsky, perhaps further removed from Schubert in culture and technique than Schumann or Brahms, yet nonetheless a kindred spirit, at least in his song cycles "Sunless" and "Songs and Dances of Death", magnificently recorded by Boris Christoff alongside his other songs. Schoenberg's Opus 15 is far more worldly and erotic yet also ravishingly beautiful and lucid, there's an outstanding recording on Naxos if you haven't heard it yet.
I would greatly appreciate an upload of the Draeseke Lieder, his work is relatively hard to come by.