This is a super easy Gallery of the Day rotator. It does it all for you including create the thumbnails. You just set it up and upload a bunch of images and it does the work once a day for you. Works via crontab to literally create a new gallery every day from images you upload. It creates the thumbnails and it pulls randomly so it will always have different galleries. When it creates a gallery it automatically moves the old pictures to an archive directory, and it will reuse these old pictures when your content runs out in the content directory. Fresh galleries, always!
