What I see here is BIG and EMPTY ... this room needs more than shelves; it needs personality. My thoughts -- in no particular order:

- Paint or wallpaper that back wall with an accent color /pattern -- I'd say something pretty bright /no neutrals. Consider repeating that color somewhere on the other end of the room -- the whole "door wall"? Maybe just around the shower? I would not do an upper-half accent -- that doesn't seem right for this room. Something like this provides color, yet also plays second fiddle to what you already have, and won't be hard to live with after a couple years:

- Crown molding would add a new dimension /a more finished /polished look to the whole room.

- I'd think about a single shelf -- black, to match the countertop -- above the toilet. Place a fairly large piece of artwork (with a black or black-accented frame) above that shelf /a small plant and curio or a little basket on the shelf. Today's trends head towards rustic, and I don't see that fitting into your room -- you need something a bit more polished. Do consider how the shelf looks FROM THE SIDE. In your space, it will show from the side.

Alternately, a train rack would work for you -- and would give you space to stack some small towels /bring in color.

Another alternate: Two large pictures stacked, though personally I like the dimension that the shelf brings in.

- You need artwork on the wall straight ahead of the door -- I'd lean towards a collection of four moderate-sized pictures hung together in a big rectangle. I like that this example is "wide" instead of "tall". I think it'd fit better in your space.

- I'd add a piece of artwork on the wall next to the right-side sink too. This example picture was rather hard to find -- this particular example is actually a concealed medicine cabinet /it opens up and gives more storage. Note that this art is important in that it reflects in the mirror /shows up twice.

- Add towel bars on each end of the tub /bring in color through towels. If you're thinking of a towel warmer, I'd put it on the shower half-wall. Be super-careful not to permeate the shower's waterproofing as you hang anything on this half-wall.

- With no good place to hang a hand towel for the left-side sink, I'd get a countertop fingertip towel stand. Or two ... those sinks are too far apart to share a hand towel.

- You need something in the space dead-ahead of the door, and you need a small stool, table, whatever near the tub to hold a book, a candle, a drink -- I'd choose something small, which would sit against the wall by the tub. This will give you something to fill that space that isn't just flat on the wall. I'd go with something black /to tie into the countertop. Another idea for this space would be a hamper. Or a chair.

- Another thing to consider near the tub: a standing candle holder.

- You need bath mats for comfort -- but with such a large space, I am concerned that they'll look like a couple sprinkles on a great big sundae. Not sure how to handle this. Maybe one long mat for the sinks? Big baths aren't easy. The sink /shower door area will be the hardest, and they're right by the door, which might catch the mat as it opens.

- Consider ditching the Hollywood lights.

- I see lights above the vanity and a light in the shower -- I like to read in the tub, so I'd really care about a light over the tub. Alternately, a carefully place sconce might fit between the window and the wall -- not sure based upon these pictures.

- Are you attached to those vanity faucets? If you change them, go with a wide-set that's easier to clean /doesn't require "flossing".

- Add window treatments above the tub to bring in color, pattern and softness.

- Add a frame to the large mirror -- this will make a big difference and is very inexpensive.

- A full-length mirror is always nice in the bathroom -- but the only place I see to put it is the back side of the door.

- Finally, add some greenery and something woven -- a hamper or a trash can? These "finishing touches" help every bathroom.