I guess you will need to be more specific for us "ceramicly challenged" (I'm a flooring gal...tile is a bit of a mystery to me). I'm guessing it has to do with the wall/ceiling interface.

Years ago I saw a publication that addressed levels of craftsmanship in construction, what is acceptable and what is unacceptable. I should have kept a copy. About that time I came to the realization that nothing is perfect, and what is acceptable to one may not be acceptable to another. There are always imperfections in anything that is man made, that's one reason we go to church. If you specified everything must be perfect on your project, then the builder may have more work to do. If you did not, explain your concerns to your builder in an understanding kind of way and see what he is able to do for you. Either way keep those bottles of vodka and chocolate bars handy.

Wouldn't be able to tell unless you pointed out something was amiss and I needed to be looking for flaws :)

Yes, the tile wall interface. If you follow the ceiling line and the tile you will see that the tile is not in line with the ceiling--it has to be cut into on the right side. Also see the other picture. The tile line slopes down in the middle like an upside down bell curve.

Had a similar situation in a 30+ year condo reno. The ceiling wasn't level. Tilers made sure eye level tiles were straight & looked good. Couldn't do much about the ceiling tile. First person that viewed the condo bought it so guess the tile job was acceptable.

Same thing happened with our self installed backsplash, the space from the counter to the ceiling wasn't the same across the whole kitchen. The lesson I learned is that subway tile is not forgiving.

The shower produces lots of moisture and the ceiling should have been reveled with cement board and tiled

This is the right way to lay tile with a slightly sloped ceiling. The wrong way would have been to have the horizontal lines closer to the ceiling or worse yet lay the tile sloped with the ceiling. The tile should be level which it is. I guess you could redo your ceiling.

No house is perfectly square, and you have to work with what you've got to work with in making things work out as best as possible. If you don't believe me, do some of your own renovations, and you'll quickly see some of the challenges the best house presents, let along older homes........

If it all was white (white grout and caulk) it wouldn't be as noticeable. No house is square (unfortunately).