hi there client,
the main concept is based on neutrat cromatics, grey and white tiles, by pulling a neutral color palet its very easy to bring other elements that will give collor, dinamics and personality of the space (decorations, asian/contemporary/modern elements like statues, vase, plants, fotos and so on), the neutral space will embrace and not reject them.
The wood, even if its white/nature oak or other wood species it will warm up the space, and make it brighter or darker, as prefered.(the guest bathroom does not have natural light so it will be a good advice to use a bright wood, also big mirrors will open up the space and make it bigger and brighter)
i can write a lot of suggestion for your remodel but i`ll let you choose your preferated design and after i am allways open to help you go further.
if its necesarly i can provide you exact mesurement, quantities, list of products, distributors etc.
also feel free to ask for dwg files or other formats that suit your needs,
tanks in advance!