I'm looking at maybe tackling this project next. I'm not going to personally do the work, but would make choices in the design.
Has anyone who has done this experienced surprises? What pitfalls should I avoid, what should I make sure to include?
I remodeled both master and guest bathrooms last year. First, get a licensed contractor. When we did the master bathroom, we used an unlicensed person who said they could do everything, and anything that needed a contractor he had people that could do that. Well, Mr. "I can do everything" turned into "Just the tile guy" when shit started hitting the fan. We also had to replumb the entire bathroom. It started with the shower drain made out of cast iron that completely deteriorated. We knocked down a half wall, but that had plumbing in it so it had to be redone. His plumber friend ripped us off big time and was really rude to my wife. When the job was done, it wasn't bad work, but I had to get the guy to keep coming back and fixing little things he didn't tie up, like the mirror being hung way too low and crooked.
When we remodeled the guest bath, we used a licensed contractor and he was great. We actually just had him do our kitchen remodel as well. The only hiccup we came across was our plumbing was illegal, they used some old piping that isn't legal to have anymore, so we had to replumb everything. This is because the previous person took shortcuts and didn't notify us when they fixed the plumbing in the master bathroom. The bathroom looks gorgeous though.
Make sure you have extra money set aside for any unseen plumbing issues. Get tile at a discount tile place, we went to Floor and Décor. We got vanities from Ikea and they're built better than you would think, and it was inexpensive. Amazon is your friend for small things like light fixtures, towel holders, etc.