Following on from M3Ucast, I wrote a new Perl script that you can use to regularly download images from Flickr using a list of tags or user IDs, for use as desktop pictures. Download it here if you'd like to try it out.
Open the file in a text editor if you want to change the tags or users to subscribe to (the easiest way to get user ID numbers is from the RSS link at the bottom of Flickr pages). Be warned that you're leaving your choice of desktop picture open to the whims of Flickr users, which might not always appeal to your own artistic sensibilities.
- Run the script, using cron if you want to run it daily
- In System Preferences, set the Desktop Picture folder to ~/Pictures/flickr
- Select one picture, choose 'Center', and set a decent background colour
- Set 'Change picture' to 'every 30 minutes' and select 'Random order'