I've done two bathrooms now. Things I have learnt:
Get as big a shower cubicle as you can. It just feels more luxurious not bumping into walls when getting in or bending down for things.
Massive baths are not necessarily comfortable, particularly if you're short - I couldn't rest my feet on the end of our bath when reclining as it was too far away! (though it was brilliant for getting loads of kids in)
Yes to grey grout.
Yes to slate floor tiles, not smooth ones.
Don't put a free-standing bath in a tiny room so you have to squeeze round it to get in 
Have a tiled splash back behind the sink please! 
No bowl sinks perched on wooden surfaces. Annoying to clean and weird.
Yes to underfloor heating - it's not expensive.
Spend good money on showers, shower doors/screens/cubicles, taps and toilets (better flush on good brands).
No need to spend fancy money on tiles, baths, sinks and shower trays.
Definitely have hand-held shower things on baths and in the shower for hair rinsing, cleaning and using as a microphone.