I didn't even know #XFCE was installable (and runnable) on Debian GNU/Hurd!
It works flawlessly (well, the file manager crashes) so far. Slow as heck on my QEMU image, but it's still really neat.
#Moka icons and the #Arc theme also work well.
As usual, I cannot easily startx as a non-root user. I need to look into this further.