Alice Lee's "hack" mosaic built for Dropbox's 2014 Hack week is a great example of how lighting can impact mosaic presentation.
Overall, this mosaic has a pretty simple technique. A layer of yellow plate and then a layer of white and black brick. But lighting the mosaic to the high left allows a significant shadow to be cast over the yellow portion which gives the appearance of an additional color built into the mosaic.
More pictures and process pics that will make you wish you had an E size printer at your disposal can be found Here.
