Types of install
For some reason, many salespeople suggest that installing tile on a diagonal makes a room look bigger. I disagree. It certainly makes it look BUSY. Sometimes very distractingly so!
My take is that tile should be functionally attractive. I believe the diagonal installation can even be disturbing, but the floor covering ought not draw the attention of the total room or area.
As for the illusion of increased size, I have come to think it is the long straight lines - the railroad track effect - that makes an area appear larger. The diagonal eliminates that option. And one can come to that judgement - or not - by viewing from a corner when there is tile already laid.