add option for randomized colors on ingested images

[t4k]

As discussed on the Drupal4Lib Islandora Code Club call, it would be great if there were an option for the colors of the ingested images to be random rather than always all the same color. This would give some visual diversity when looking at generated content.

[mjordan]

This would be a neat feature, and would be easy to implement. I'd be happy to lead the d4licc through coding it in a meetup. I can't make Sept. 10, but any time after that is good.