First of all--cut down the size of the bathroom. My master bath is 9x12.5 and I regret every wasted square inch of it. It's unnecessarily large at the expense of the bedroom or more storage.

I also wish it didn't have a whirlpool tub--useless. I haven't used it 10 times in 15 years (it was installed as I was buying the house and I didn't have any options by that time, everything was installed).

You need to hire an architect/designer. They can lay it out with usability and plumbing in mind.

You can post your floor plan over in bathrooms, and folks will help you with it.

Are there any restrictions on where the toilet can go? Moving waste stacks and adding wall toilet plumbing is a hefty up charge. Are there any windows in the room? I have a similar size bath 13x8 but unlike tatts, I think it is a nice size but I put in loads of storage, a cushioned bench and a nice sized walk in shower instead of a tub. You certainly have room for a tub and walkin shower with a single sink and less storage though.

Like the gray rectangle tiles. Don't like those that are not smooth -- cleaning nightmare in the making.

Bathrooms need "storage", too -- laundry hamper space in addition to storage space for toiletry items -- and don't forget that plunger and cleaning supplies. You also need an enclosed towel cabinet as far away from the steam of the shower as possible but still inside the bath for convenience. A full length mirror behind the door with a hook over that for a bathrobe is also a good idea.

One option:

3' depth to put your shower/tub combo in the 7' end of the room.

3' for toilet. (Note: choose the mid-height rather than the shorter one.)

5' for vanity

3' for door clearance. (You've marked it at 3').

+_____

+14' total.

You need a 3' path out of the 7' width for the length of the room for walking.

You need about 3' from the wall for the toilet, back to front, leaving you 4' of the 7' across from the toilet -- room on that wall for towel racks near the tub.

A vanity will be about 18" deep, leaving you 5 1/2' feet -- 3' for walking path and 2 1/2 for another feature.

Across from the vanity, add a 18" countertop and overhead cabinets the same length. The countertop can be used as a dressing table and/or a place under which you can hide a laundry hamper. You'll also find it useful as a place for setting your clean clothes as you shower.

Across from the door, add a floor to ceiling cabinet 18" deep for towels.

If you can add a window above the countertop between the overhead cabinets, do.