Square or Diagonal

I stopped by the house this morning after a long dentist appointment. This was the 3rd morning in a row I stopped by, and the 3rd time in a row my visit was productive. Today, I reminded the carpenter hanging doors that a bathroom door was one of the few "normal" thickness ones (most of our doors are 1-3/4" thick, heavier than standard), and talked to the tilesetter about how to put down tiles in a shower floor.

Square or diagonal? Square makes more sense, everything in this bathroom is square, but I like diagonal. This is why I need interior designers.