Matt tiles. I cannot bear the watermarks on the tiles left by previous numpty owner. Second the decent extractor. Bathrooms pong due to constantly being slightly damp and the paint peels off the ceiling. Eww. I wouldn't go for floor to ceiling tiles unless you're the type to be bothered to clean them. I'm not... Plus, I think that if you have some paint in your bathroom, then you always have the option to change it with a lick of paint in the future.
Stay away from shiny stainless steel, again, unless you want to keep polishing it. In a family bathroom, this could take up a lot of your time.
Get a shower head that is not attached directly to the wall in order to aid cleaning of shower. If you have a separate bath to the shower, I really like hte set up in one of our bathrooms where there's a bath with a nice shower attachment low down near the taps which means you can take the shower head out and rinse your hair whilst having a bath (and trying to ignore the splashes on the navy shiny tiles...)
If choosing shower doors, look at the joins and crevices and buy ones that aren't going to gunk up really easily with limescale. Even better, get frosted ones so that every drop doesn't show up immediately.
Ummm, oh, toilets. If you're getting a new one, I really like the ones that sit up off the floor so you can mop/ clean underneath them and you don't get muck/ dust round the base of the loo.
If you get a "concealed" cistern, make sure you have some way of getting to the cistern without taking tiles of walls etc. (See earlier comment on numpty previous owner of house.)
Simple other things, like don't have the base of your over sink mirror too close to the sink as otherwise it will be constantly covered in splashes. Same with shelf over sink if you have one... My mirror is constantly splashed because the shelf with the soap dispenser is right in front of it.
Think I should be quiet now.