I would bring it up with the contractor immediately.

If you can get a hold of any of the tiles that haven't been set, take a look at them. Sometimes you get a batch that is pretty warped. But having said that I usually make sure to show the GC or homeowner and get them approved. Also the worse the walls are out from being flat the more it will accent the 'warpedness' of the tiles if they are warped.

It looks kinda rough to me. I would talk to the GC about it.