Since I already posted the xscreensaver pipe menu, and my script to change wallpaper is basically the same, I might as well mention it here.
It’s in the Arch pastebin here. The script is almost identical, with the omission of a “Stop xscreensaver” command at the start and the DIR and CMD variables changed. I also removed the ARGS variable, since feh doesn’t need any trailing arguments for this purpose.
Once again, credits go to this post in the Gentoo forums.