You can have your vote here:
http://www.jpl.nasa.gov/dawn/world_c...poll-20150424#
My money would be on ice but the information I'm basing that on is pretty thin!
Keep in mind that those bright spots are really only bright compared to the very dark surface of Ceres.
Exciting times though!
EDIT: there's also a thread already going on about this here:
http://www.iceinspace.com.au/forum/s...d.php?t=134209