This is pretty much just slapping up tile. The problem is that it can only be done on a weekend due to time constraints. Once I mix up a batch of mortar, I'm pretty much committed, and there's not enough time after work to do it. So it's going slowly.

Left wall.

Back wall. Notice the tile with the hole drilled in it for the bathtub faucet. The pipes didn't line up with the seams like I thought they would. Fortunately, there were some diamond hole saws for sale at Harbor Freight (Home of the Disposable Tool). Put one in my drill press, used a spray bottle to squirt water on it every few seconds, and it sliced right though the tile in a few seconds.

Right wall.

This is where the sink/vanity will go. It also shows the effect I got from spreading leftover mortar on the walls. It should look really good once it's painted.

Upper left wall.

Upper right wall. At this point, the only remaining full-size uncut tiles I have to set are the three around the shower. Everything else will require cutting. Plus one more hole for the shower. In particular, fitting around that window will be fun.
You'll also notice a pair of adjacent missing tiles in the corners. Those are for shelves, but I need to cut holes for them. The shelves themselves won't go up until the grouting is complete.
Finish setting tile