In a bath like this one there was an extensive amount of planning, but the first decision was to to create a clean contrasting look between the white marble and the dark cabinets, then they decided they wanted to bring in some additional colors through earth toned sinks, tub (massive hand carved one that matches the sinks (about where the photo was shot from) and wallpaper. If you are starting from scratch and a bit lost, I suggest picking larger item(s) to set the tone (typically a tile you love or color/style of the bath fixtures) then build around those as your design moves forward