A fun way to pep up black and white pictures is to modify the colors of the picture. For instance, take this iconic picture of Che Guevara. is is based on a black and white picture. I replaced white with red to to achieve the look of the well know version of this image.
Replacing white with red is not the only option. Using the brightness a white or a black image for the RGB channels allows in total 64 variants to combine into a colored picture.