We converted our small downstairs loo into a wet room at the end of last year so am happy to share my views if they may help.
Similar to you, though not the same, we did ours for use by someone with a disability.
Tiles on walls - we opted for large, light coloured tiles with a matt finish the rationale being less grout to go manky and no background gloss to show up those pesky watermarks (very hard water here).
We did put in some border tiles to break it up a bit because we have quite high ceilings.
Paintwork is white in order to keep the room light.
The floor gave me sleepless nights when it came to choosing what to have.
I was leaning towards non slip tiles but my plumber advised against it as he said the grout on floor tiles is the weak area and if the grout fails you have water seeping into your floor and being on the ground floor, you wouldn't necessarily know about it until it caused major problems.
Suffice to say, he worried me enough that I went with his recommendation of wet room vinyl called Altro - See www.altro.co.uk for colours etc.
A shower former set in concrete (?)goes down first.
This has a gentle slop in it and the slope directs the water to the drainage hole.
The floor fitters then put down some sort of screed and laid the vinyl over the whole room, forming curves at the corner of the room and going up the wall slightly to about skirting board height.
There is a narrow white strip which covers the join where the wall tiles meet the flooring.
My main concern was that it would look like an institution type of floor but in reality it looks gorgeous, is very safe to walk on when wet and is very practical.
I also lost much sleep over what to use to stop the whole room from getting soaked.
Because it is a very small room, a fixed shower screen wasn't an option.
I looked at the possibility of a fold away screen (or 2) - See www.outasight-vb.com but the logistics of it wouldn't have worked for us, so I ended up with a shower curtain which was made to measure (those high ceilings were the problem). I got one that was weighted, thick and heavy etc so it doesn't flap about when wet and stick to your body.
We did fit underfloor heating (thanks to Mumsnet!) but DH wanted a radiator (thank God) and as we couldn't agree which we should have, we had both.
Personally, I find the underfloor heating is useless at heating the room, though I suspect we don't use it properly, but it does take the chill off the floor (just about) and helps it dry out a bit.
The radiator keeps the room very cosy.
A stainless steel toilet roll holder fitted inside the shower area doubles up as a steadying grab rail/handle once the loo roll is removed while showering and a curved towel rail fitted round the radiator serves the same purpose once showering is complete and the curtain pulled back.
We have spotlights too for brightness and a reasonable extractor fan though the room does have a small widow in it.
Good luck with it all.