This dialog lets you view all the pictures that have been used in montages (thumbnail mosaics, postcard piles, etc.) for switching recently - whether they be mosaic images from Flickr, montage images from your own photos or whatever. You can double-click on the thumbnails to go to the source pictures. Simply pick the cache from the drop-down list to browse the pictures and find the one(s) you're interested in.
You can control how long pictures are cached for in the Picture Handling section of More Settings.
See also:
