Tiling a wet room i would not recommend for the novice tiler. I have been asked so many questions about wet rooms from tilers and even shops, They mainly fail due to the correct procedure not been followed, now somebody said on here use moasics yes look great and easy to apply but you need to know what your doing, it must be primed well and 2 - 3 coats will not go a miss either to the floor. Now we all know that grout is very porous and the more grout joints there are the more water can escape to the subfloor if not grouted up to spec. Even the best grouts absorb water even in swiming pools. Downstair wetrooms are no where as bad as upstairs because if they get a leak there not going to really know about it unless the tiles start failing. Also one last note is that when installing mosiacs you can not get a really thick soild be of adhesive down and depending on how thick they are your looking at 3mm - 4.5mm notched trowel max which would give you about 1-2 mm soild bed.
Hope this helps