Use different wallpapers for each Space
From Lifehacker:
Mac OS X (Leopard) only: Virtual desktop enhancement utility SpaceSuit assigns separate wallpaper images for each Spaces virtual desktop so you can distinguish between desktops at a glance.
From Lifehacker:
Mac OS X (Leopard) only: Virtual desktop enhancement utility SpaceSuit assigns separate wallpaper images for each Spaces virtual desktop so you can distinguish between desktops at a glance.