I agree moving the toilet will give you a much better space if it's possible. I find it gross to bathe in a tub so very close to a toilet - especially with 3 teen boys using that toilet! It seems like a pretty small bathroom, so trying to fit a wall-length counter in doesn't seem like the best use of space. Since the tub must be at least 60" long I assume your bathroom is about 60" to 72" long - you could change the layout to have a vanity with plenty of storage and adequate counter space (somewhere between 30" to 48" vanity) and have the toilet on the far side of the vanity (allow adequate space on either side of toilet for ease of cleaning), attach TP holder to the side of the vanity and then use floating wall shelves or an over-toilet cabinet to give them additional storage, then towel hooks or bars go where the toilet is now.

Oh. Like magic. :o) For sanitary reasons, I’m not sure what you could put there. How about a couple of floating shelves on the wall up above? If you don’t need the storage/display space, I still think just an art print would do it. It is a bit of an awkward spot but its location right next to the toilet kind of gives it an ick factor. Sorry I’m not more help.

I agree just paint the trim white and even the inside of the door . I will however say a kids bathroom to be used by guests is a bit awkward unless the kids can be forced to be extra v\clean and tidy when you have guests.

Well it depends on the size of the transom. A traditional transom will not. if it is a larger and or operable transom possibly. A lot depends on your ceiling height as well as the outside elevation with that. If light is your goal you can do both if it works on the outside elevation. Also you can do a regular size window inside a shower. Or two smaller square windows.......the possibilities are endless but I try to not elimate existing windows where possible especially when it gives the opportunity for function and light. lower cabinets although tall ones.....i would go counter height with window above.