A light blue or green with grey undertones would look lovely. Bright white trim to tie to the bathtub.

Great job, looks great! As far as paint suggestions: Benjamin Moore Nimbus is a really pretty soft gray that can be either warm or cool depending on your lighting. BM Light Pewter that is a very light gray. BM Pale Oak might work for you too since I see the contrast between your tub and tiles reveals the tile has more warmth than the white tub. If you are looking for a white, Sherwin Williams Elder White is a warm (but NOT yellow or pink) white.

Regardless of what you contemplate, ask your paint store for their LARGE swatches and when you get it narrowed down, get a pint and roll it out on a poster board so you can move it around different walls in the AM, midday and PM )

Your tile looks like a some of the tiling I was looking at for our at-the-moment bathroom remodel. What is the name of your tile if you don't mind me asking.....I need to make my selection in 3 days.

I like what you've started! I think a grey trimmed in white would go great with your tile.

grey would look great.. but nothing light. something darker to give it a good contrast.

I have SW Silverpointe in bedroom. It is a very light grey with green undertones. It's my favorite color in the house, but it was too dark for my bathroom because of lack of natural light. In bathroom I used SW Crushed Ice. It is in their whites collection but it's a very light grey with just enough color to make the white trim show up.

Light grey would look very nice! Love the marble!