You want a drain that has a removable cover if possible so "debris" (you know what I mean) can be easily washed down.
Do not make a recessed covered cabinet or whatever in the shower--it will get moldy and mildewy because it will never dry. That's not where you want to have a hiding place for goodies. Besides, your housekeeper will undoubtedly find your toys and equipment there.
You definitely need an extra valve/spigot or two for a hand shower so you can pop a shower shot on and off, not to mention colon tubes, etc. The hand shower is also good for rinsing down the entire shower enclosure so you don't get soap scum build-up.
Tile the ceiling in the shower also. Do ALL tile/granite/marble, etc.
Do two seats or a bench where two people can sit under the shower---relaxing on lazy days. The seat back should be angled slightly like on a chair, not a 90 degree wall so it is comfortable to lean back against.
In addition to auxiliary needle shower heads and hand showers, it is nice to have TWO regular shower heads side by side so two people can shower under their own shower heads on the normal days where you both have to get showered and dressed at the same time, although this may not be possible in a 42 x 60 shower if there is a seat or bench to sit on. If you can, a 5 x 7 or 5 x 8 foot shower enclosure starts to open up real possibilities, among which, you can lay down with room to spare. (You can put down a foam yoga mat if the tile floor is too hard for you. They're easy to clean in the shower and dry pretty fast.) A shower that large needs TWO floor drains. One that size also allows you to use real colonic speculums obtaining an endless water supply from the hand shower hose (input) and have the feces waste line (output) go right down the drain.
The color of the tile or stone doesn't matter. Pick something classic if you use ceramic tile since you will hopefully be living with this for many, many years. With marble and granite, they are all classic because the rocks have been around for millions of years!! The color of the grout should be moderate so it never looks stained. You do not want the enclosure to be clinically white. Some day you are going to sell the house and spending $40,000-50,000 or even more on a bathroom that looks ugly to potential buyers is not a good idea.
Make sure that all corners (walls, floors, ceiling, etc) where there is a change in geometric planes are silicone caulked NOT grouted. This will ensure years of leak free performance. DO NOT grout and then silicone the corners. That isn't the same and it is third rate construction, unfortunately, many contractors do that. ALL caulking must be completed and dry before grouting is done.
Believe me, I do know what I am talking about.
By the way, if you get a bidet, get an American Standard, NOT Kohler. Not that I have anything against Kohler, but the American Standard has a diverter valve that allows water to flow through the rim of the bidet seat so you can warm it up before you sit on it in addition to the fountain spray. BUT you should check this out with your local plumbing dealer. When we were building, that's how the bidets were, Kohler might have bidets that have water flowing through the rim now.
One final thing, you might also think of adding a steam generator.
Have fun with your project.