From what I know, no. At least no for the moment.
I know that you can import from other games or create in a 3d packeges static assets like a fence, a trunk, or a stump, but everything that requires animation is a bit tricky, the game uses the same animation system that WoW (Granny3d) and it's propietary software with their own format (.GR2) so we won't be able to tweak animations, attach helmets or hairstyles to the proper skeletalbones, nor create our own monsters/animated objects.
At least not for the moment, the Wiki says they are working on a Maya exporter, but I don't know if that implies getting things into maya and being able to change them back, or if it's just an exporter from Maya to the type of files the engine uses, and if that format would accept animation like FBX... Lots of things we don't know yet.