Floor tile murals, is this proper?
The pictures show a beautiful job so far. 

Grout lines that are too narrow make tiles that have some size variation very obvious. In addition somewhat wider grout lines allow some minor tile misalignment to be accommodated without it sticking out like a big thumb. This includes variation in the tile X&amp;Y dimensions as well as small variations of the laid height of the tile.

I suggest that you are very observant right now as you are forking over good money to get this installed. I would venture to guess that after the installation has completed and you have walked over it a few hundred times that you will be completely past any concerns that you have today.