I've put together a bit of code that displays a chosen number of new and/or random images from your plogger beta 2.1 gallery. I originally wrote this for my own gallery, and wasn't planning on releasing it, but with the number of requests I see for random thumbnails I thought someone may find it useful. It's fairly straightforward, but use at your own risk and back things up before using... it's only been tested on my site.
This began as a modification of niceday's random thumbnail code, and still relies heavily on his class framework (his code appears to no longer be available): http://www.plogger.org/forum/comments.php?DiscussionID=76&page=1 The code from theg3nius was also very useful: http://plogger.org/forum/comments.php?DiscussionID=77&page=1
You can get chaosthumb here: http://www.solemnchaos.net/2007/01/chaosthumb-displays-random-and-new-thumbnails-from-your-plogger-gallery/