Curb movement like that is typically from a wood-built curb (stacked 2-by lumber, for example) that is absorbing moisture and expanding/swelling. How is moisture getting to the curb? Could be one of several things. Not sure how conscientious the installer was in terms of making sure the shower pan membrane is sloped (versus laying the membrane flat on a flat subfloor), or how he detailed the membrane over the curb. It's possible there are nails through the top or inside faces of the curb (and thus through the membrane) and moisture is getting through the nail holes. It's possible that he built you a perfect curb but used wet pressure-treated wood and the PT wood is warping as it dries. Or your house is on a slab, and he put the wood right on the slab. Moisture through the slab is causing the wood curb to expand. So it could be one of several things. It should be fairly easy to diagnose though, as the tiles are popping off on the outside face of the curb. They'll have to be removed eventually to diagnose and repair. When they are removed, take a look to see what's in there. Post photos if you can. To give you a bit of an education as to how a typical CPE-membraned shower with a wood curb is built, check out Harry's pictorial. Note that Harry's membrane is "draped" over the wood curb. That there are no nails/screws on the top or inside face of the curb. That the lathe (wire mesh) is bent in a "U" shape and it's simply the inverted "U" bends that hold it over the curb. Again, there are no fasteners through the lathe and into the top or inside face of the curb. I have seen instances where the membrane gets draped over the wood curb, then the installer nails cement board on the three faces of the curb and tiles on the cement board. Not good. Again, nails through the membrane on the top and inside face are a no-no. I don't see screws through the bottom track of your door frame that go into the curb. That's good. Best, Mongo

As you can see, these are pros commenting on your post (I am not). These particular pros are very well known on this forum for their good sense. Since you seem very focused on simply choosing the tile (and do not seem interested in changing anything else in this tiny space), I think that if you want something just to be an improvement over what you have, and you are worried about aesthetics, then you need to re-read my response above recommending that you take the hallway laminate sample to an actual tile store for help in person. I stand by my advice for a neutral, warm color with matching grout. And yes, I do agree that this bathroom is due for a total re-do. You have to actually SEE the tile in person. Even if you order from the internet, you should see a sample first. And your floor area is so very tiny, that almost any tile you choose will be reasonable in price. If price is a major concern, then perhaps you can also consider a simple, white solid sheet flooring. It would be easy to keep clean, and probably the easiest to install (I'm told).

If you retile the floor, it enables you to increase your Zillow listing value - under the category of last year remodel. Yes, you could leave it and allow the new homeowner to do the work themselves, but with so many wanting "move-in ready" ..... (And....Let's face it, most younger homebuyers were at soccer practice or playing video games, rather than helping with yard work or car/ home repairs. So, they know nothing about "how to" around the house,). New Tile Color-. I'd pick a light/-medium gray tone in the countertop. Black will show lots of dust, White might be hard to match to your cabinet color. Perhaps the one closest to the tub? It hard to tell the color for certain. What at color is the bathroom wall? If white, then paint trim to match gray floor.

If you have a curb, you will have the cracks develop there, too. and where the walls meet the floor. Anywhere where two different materials meet or where one surface meets another that is in a different direction (known as "change of plane"). My contractor still grouts such places, too. But I did a solid surface shower that he could not do wrong. I am keeping an eye on the place where the floor meets the shower pan, all other places are in dry areas. So there it is just cosmetic. I would guess that water can get behind your tile with those cracks. If properly waterproofed it is fine, but if not, I would get to this as soon as you can. A lot of shower builders do not use waterproofing, even though it is now required. If you do a search on this forum for "Shower waterproof," you can see many discussions about it and learn what is and is not waterproof. (Redguard yes, Durock no, for instance.)