So I feel like I need a few disclaimers to explain how this brain works! :-)
I feel like the style of the lake house is part "spanish revival" part "rustic" and from what I'm gathering..we're trying to add some part "classic contemporary". That being said, I attached various pictures with comments below them. The pictures themselves don't represent what I like, but rather represent some idea or concept that could be utilized for inspiration. And then some pictures I just thought were neat haha so I put them in too.
I personally love the style of the cabin and would try not to infuse too many modern elements because that's what makes that place so awesome...Not to mention, you can do that with furniture and decor. HOWEVER...that's just my opinion : ) I know we all have different styles which makes the end result so fun, because it's an accumulation of ideas.
Now, I'm not sure what ideas you decided on as far as the theme of the rooms and coordinating bathrooms, so don't be scared by some of these pictures! I had heard some ideas about various color schematics as well as perhaps a 4-season theme...very fun!
I also have no idea what is exactly being remodeled in the bathrooms, but just thought maybe this could serve as a starting point for inspiration as far as tile & tile design go.