The following syntax are supported
$HOME
${HOME}
XMonad Wallpaper scans user supplied directories by detecting their mimetype rather than rely on extension
cabal install xmonad-wallpaper
import XMonad
import XMonad.Config.Desktop
import XMonad.Wallpaper
main = do
-- Randomly pick a wallpaper from
-- directories specified as wallpaper
setupRandomWallpaper ["paths-of-your choice", "$HOME/Pictures/Wallpapers"]
xmonad $ desktopConfig
{ terminal = "urxvt"
, modMask = mod4Mask
}