Again, this is preference. However, I chose to do the shelves first before because I had the material for the shelves and was still waiting on the extra boxes of tile I needed. Also, I found it easier to drill the shelve supports straight into the studs instead of having to go through tile and risk breaking them. Another main factor was the lighting. because they are ran through the shelves and into the wall, I would have had to make a large enough hole in the tile for the wires to go up and into the wall.