I'm about to make a site wide change on my websites galleries, so that popular items are first in the list, vs the current setup, which displays the latest.
This will improve bounce rate, as much better content will be shown as default. It will also help prevent mass uploaders, from taking over the galleries.
Now, how to deal with the newer content, that obviously needs to be indexed.
Our sorting options, are currently loaded with Ajax to prevent Google from seeing them. The URL doesn't change either.
My feeling is to create a text link, that leads to a URL that displays the content in date order, and has a canonical tag, back to the main URL which is in date order.