This is some really detailed concept work, the fact I can distinguish every single object on the tables shows the amount of work that must have gone into this piece.
As well the perspective and floor details are so bang on it makes it seem like this was a black and white photo of an existing tower! :D
The one thing I will point out that seems a little bit off is staircase #2.
I'm sure it was left like that to simply show that it leads to the other part of the tower, but as it stands it looks super steep and crooked, making for an unsafe work environment for the resident warlock.
Going over and doing a quick fix for staircase #2 so that it doesn't seem quite so steep would make this concept piece pretty much perfect.

Excellent work all around. :P