Put a lamp and a potpourri grouping on your vanity counter. Use other small groupings throughout the bath to break up the straight lines. Colorful hand towels work well by the basin, creating little splashes of color. Almost anything that breaks up the planes of the bath is good. One idea that works well is a simple stack of towels by the tub along with some nice greenery.
Candles work especially nicely by the tub.
Think romance and comfort. There are as many small touches for the bath as there are ideas in your head. Candles are especially nice alongside the bath tub.