I hope to someday put together a tagged database of figures pulled from the geological literature that may be useful to others, primarily maps and stratigraphic columns. For now, though, I am sharing an Evernote notebook to which I will be adding over time. It can be accessed here:
https://www.evernote.com/pub/matthewbk/publicimages [EDIT: No longer. 2014-02-04]
Future plans include tagging the images (type of map, area covered, stratigraphic units) but I am not sure of the platform to use. Tumblr, Blogger, or even Pinterest (in addition to the possibility of Drupal) are all possibilities at this point that will allow collaboration.