I would use egg shell..semi gloss for me is reserved for the trim

First of all, I would consider using bathroom paint for the mold problem. A few years ago, I made a huge mistake by allowing the paint guy to put anti-mold stuff in the paint I had chosen for my bathroom. Turns out it is for outdoor use only. It had a heinous smell, and I had to paint over it several times just to mask it. I think it was about 5 years before the smell died down. So, don't let anyone talk you into that. Use real kitchen and bath paint! Next, I don't see any reason to paint over the green tiles. I'm not a huge green fan, but if they are ceramic tiles in good shape, then painting over them may not be an improvement. It seems to me that a sandy color or medium ivory color paint on the walls may do well.

Slate tile is a great choice. I have it in a washroom and we love it. But it does tend to feel cold underfoot. Any chance you are considering under floor heating in that bathroom. We got brushed slate, which means that there are no rough edges or shaling going on. We got a dark grey colour but I also saw it in other colours, lighter grey (almost a greige colour), a green colour and some that was closer to black but had some significant rust colour in it. If you have a look, you should find it easily and it came in many sizes as well. I like something like 12 X 18 or 12 X 24 tile for flooring. When you say you want to use it in the shower as well, do you mean on the floor of the shower? If so, then you'd need much smaller tiles for that to accommodate the slope needed towards the drain in the floor. But you can likely find the same stone in smaller tile sizes. I recommend the brushed slate for the smoothness. Some slate I looked at I felt the ridges were enough to catch your toe and some were quite sharp feeling as well. I think that could look really fantastic with a white subway tile. Have a look at some of the handmade looking tiles. That might go really nicely with the rustic look of the slate tile for the floor. Have you chosen a vanity? We went with a pearly grey colour and that was the colour of grout we used as well and it looks great.

My opinion will be biased because I have very similar tile in my master we redid 12 years ago. 4" squares on the diagonal for the shower floor and 12" squares on main floor and up the shower walls. Coincidentally we are in process of redoing my kids' bath the past few weeks (it was also redone 12 years ago) because a hard-to-find leak in the tub prompted us to consider replacing it....which then brought about the issue of replacing the tiled tub-surround that would be damaged...and we would also have to try to retile some spots on the floor because a new tub would be a smaller footprint leaving some bare spots once old tub was pulled out. My point is that we also had to figure out the whole, "do we do an updated 'patch job' to save a lot of money, or do we just gut it and accept the cost as the price of being at peace with it/enjoying a new look and improved function. Right or wrong...which is always a very subjective thing....we gutted it and I'm thrilled. I was not interested in painting my cabinets just to have them have peel-issues due to steam, and we also got rid of the tub altogether and opted for a stand-up/walk-in shower for my older kids. Resale was considered on this issue...but by the time we move, someone can either love it as we've made it, or we will price the house with an "allowance" in mind. The old space had hot-chocolate colored walls and 'slate' porcelain floor and tub surround...an overall warm and cozy feel but also tired and dated. The new space is a porcelain 'marble' hex with white subway walk-in shower that is awaiting glass doors...an overall calming feeling that is also bright and fresh. I now actually wish SO BADLY that I was able to redo/retile MY whole bathroom (tile similar to yours). And there's nothing wrong with my bathroom, and a planned paint job on the walls will help me like it even more...... In my kids' bathroom, however, even unfinished with the floor and shower tile installed just waiting for the rest to come together (waiting on backordered tile base moulding) ......... I walk in and just smile and breathe deeply because of the way the space now makes me feel :) So my very biased vote is to gut it ;) ;)