I like to keep an iPhoto library for wallpaper. But iPhoto doesn’t sort by resolution! This is bad for anyone with multiple resolutions. So… I wrote a script for it! Open iPhoto, select the photos you want tagged, and run the script. Poof! your wallpaper will now be tagged (in description, not keyword) by what device they would be good for.
You can also edit this script pretty easily to put in your own hardware tags.