Do a search on Houzz for backsplash tiles to identify what you like. Then go to a good tile showroom (not the big box stores) to see them in person. The showrooms usually have sales people with some design ability on staff (it's hit or miss unless you go to a very upscale showroom like Artistic Tile, Walker Zanger, Ann Sacks, or Waterworks). They can help you. But keep in mind that simple is best. Pick one tile for the walls and a complementary one on the floor, including the shower floor. Stick to porcelain or ceramic--they'll usually be less expensive than natural stone, and easier to care for. And find a line that has multiple coordinating tiles for ease of selection, since you are doing this yourself and have that religious aversion to hiring a designer.
As others have suggested, look at as many pictures of bathrooms as you can and save pictures of the ones that you are instinctually drawn to. Then see if there is a common denominator. The good news news is that since your space is small, you can splurge on getting materials because the cost of is not going to be significant as opposed to a larger space. I just finished a remodel and i didnt I didn’t want the gray or beige boring spa look that is currently on trend so I used color and design and I loved the end results. I would suggest going to the best tile stores you can in your area because the staff people can probably offer better design advice than you would find at lower end stores and the actual tile choices are breath taking in their possibilities. You can also google and check out websites of the betterctile companies for inspiration in their galley photos. Some choices have been suggested. There is also Encore, Motawi, Pratt & Larsen, Fireclay. Check out Mission Tiles. My bathroom was done using tiles from Encore, Pratt $ Larsen amd a marble design from Artistic Tiles
Not the mirrors but the shower.
Floor walk in
like the shower wall
like the shelf between double vanity but don't care for bathroom