There isn't a whole lot you can do to make white look interesting. Two ways I could think off was to vary the tonal quality of the white clothing (i.e. whites vs off-whites) and to create different fabric textures via paint (i.e. diaphanous vs stocking vs cotton). So that was what I did in the painting of Suicide Squad Katana's white clothing, work-in-progress photos of which you can see below.