My shower is 37x48 and has a bench, rain head and handheld.
A foot rest is about all a corner bench is good for. I would put in a bigger bench.
I would put the rain head in the same place as the previous location ( it doesn't have to be centered) and the hand held further in on that long wall. I think the controls should be located under the niche as shown and the door should open on that end. If you put the controls on the short back wall you have to go all the way into the shower to turn it on. That's not so good if you want to turn the water on for a little bit before you get in. I think a bench along the length of the short wall would work just fine.
My bench is 37x13. It does not go all the way down to the floor. It is more than enough room to sit on if you want to.
Here is my set up:
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I agree that it is good to have the shower control as close to the door as possible. It is nice to let the water warm up before you step into the spray. Whether you do a corner bench or something along the back wall, I suggest you do it with open space underneath as shown in badgergal's photo. It will feel less cramped and less likely to stub your toes.

I would have a concern about the moisture trap under the open bench. All kinds of things can grow there in the moist and dark. Since I am the one who cleans it, (and I am no Spring Chicken) I wouldn't want to get on my knees to scrub up under there. It is arms that flail away in a shower, washing hair rinsing arms, and the feet get put up on a bench to soap up legs and toes, so I cannot imagine needing the foot space under the bench. I've had a solid bench in my old shower for over 40 years and I never sat on it once. I guess it all depends on how a particular individual uses their shower. Build it the way YOU want it. Most important...don't put the showerhead where it will be directed at the door, and as stated above, put the controls near the door.

-Babka

I'd have the valve located where the others have mentioned, where you can open the door and turn on the water without having to step into or reach through the shower head flow.

If required for space, I'd consider moving the niche deeper into the shower so the valve can be closer to the door.

I'd recommend having the rain head centered on your short wall. It can be centered or a few inches deeper into the shower on your long wall.

I'd place two can lights in the ceiling, offset on either side of the rain head.

I wouldn't use a built-in bench, or a built-in foot rest. I'd rather have a movable 3-legged stool. A stool can be used as a footrest, or pull it in the middle to sit under the rainhead, or if it drives you buggers move it out of the shower completely. Though I make them out of teak, they can be purchased too. Wood is usually more comfortable on skin than tile.

Though I make them out of teak

Do you have a picture of one you have made? We bought a 3 legged stool, but I am not happy with it. Maybe I should add making one to my husband's ever ending list of projects.