Pick one of the colors in the vanity top that you really like, and use that. With the bronze fountain and bowl, probably one of the softer dark browns. Or if you really want an accent, pick a dark red in the same color family, i.e. a deep burgundy or red. That however would not go with the green towel. Where were you putting the accent color? What color is the floor?

The floor is a dark brawn hardwood. The towel is just temporary until we find the right colors to use. Accent colors would be towels and some wall hangings.

How about some wall art you like and pick a color from that? Or a small area rug? With your neutral palette just about any muted color would work.

Find a picture you love, bright towels and rugs that the colors are in the picture, and go for it. My bath has an old blue tub, but I did the walls in a light burgundy and a floor of white inlay with swatches of blue, burgundy and sea foam green. Vanity is oak and has a blue & white marble top. I can use burgundy or Teal towels and they go great. Your bath is very neutral, so pick your favorite color and go to town. Get some paint swatches and put them around to see what you like in colors, that will help you decide.