The trend is towards bold deep colors for the walls to make the space dramatic. Accents of compatible complimentary colors can be used for bath towels or a striking art piece. A vanity bath is a super fun place to use metallic and specialty finishes.
I have always enjoyed fun bright colors with a theme. Turquoise walls with white cabinets and yellow towels along with undersea stickers of fish and maybe even Spongebob Squarepants.
Warm tones and lighting are important for makeup and getting ready to go out.