I used 4 x 12 white subway tiles in my 5 x 8 bathroom, including the walls of the tub/shower combo, and I love the way it looks. I also used 4 x 12 subways in my kitchen, 15 years ago, so I knew I liked the look. Of course it would be different inside an enclosed shower, but you would still have the advantage of less grout and more nice white blocks of ceramic. In a small shower you might have to cut too many tiles to go around the corners, but since your shower is close to the size of my whole bathroom, that would obviously not be a problem.

We're using 4x12 subways too. Do a search for catmom's pictures to see an example of that size of tile.

We originally picked a 8x20 subway that we really loved, but the only trim offered to go with that tile (expensive long qtr round) would have bankrupted us.

We used ~4x12's in two bathrooms (same tile, had it installed vertically in one, horizontally in the other), and 8x20's in the third bathroom (had White Thassos marble tile cut down to use for trim rather than the bullnose tile that went with it). The shower in the first bathroom is only 3'x4'.

We decided to set large 10x16 subway tile in a vertical pattern to create an illusion of height. Our steam shower ceiling slopes down, so we decided the vertical arrangement will help compensate for the low ceiling height on the North wall. Our designer suggested large tiles instead of several smaller options; she warned the overall layout would appear very busy and out of proportion if we used small subway tiles in our larger space.

Here is a link that might be useful: Master bathroom renovation underway...

I think it will look great. It better! I'm using 6x12 tiles in a subway pattern in my shower as in this first shot, the second and third shots are pics of showers with large subway tiles from houzz.com:

{{gwi:1403101}}

[contemporary bathroom design[(https://www.houzz.com/photos/contemporary-bathroom-ideas-phbr1-bp~t_712~s_2103) by dc metro kitchen and bath Case Design/Remodeling, Inc.

[contemporary bathroom design[(https://www.houzz.com/photos/contemporary-bathroom-ideas-phbr1-bp~t_712~s_2103) by vancouver interior designer Claudia Leccacorvi

6x9's a horrible in a running bond pattern (brick work). Their length is not proportionate to their height.