Thomas Huth, and myself are organizing the 2016 edition. We still have a couple of slots left, so don't hesitate to contact[1] if you have a cool disk image (or two) to contribute!
Edit: Check out the original announcement[2] by Thomas about disk image requirements.
[1] http://www.qemu-advent-calendar.org/2016/#contact
[2] https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg039...
I would love to see a qemu image for any of the following:
1. E2 (Erlang OS)
2. TempleOS
3. That new OS Google is supposedly working on
Corman Lisp/Clozure CL/SBCL Common Lisp Interface Manager https://github.com/robert-strandh/McCLIM
meta emu: b-em/atomulator/elkulator/rpcemuspoon/ep128/amstrad cpc/fuse/stella/atari800/hatari/vice/uae/apple II/kegs/basilisk/sheepshaver/vmac/psx/pcsx/mess/EACA Video Genie etc. A lot has compatible FLOSS ROMs included.
sky is the limit: Stellarium