Doesn't seem to work on my blog. (wp2.9.2)
Custom Post Background correctly appears on post edition dashboard.
Choosing Image from URL but after validating post update with background picture defined still have "Address Web Source: Disable" !
Picture is stored on same blog's host and url checked.
Btw, when tested with "Image from media" only got a list of two pictures amoung more than 9000 in my blog gallery....
Is there any parameters or anything else to tune before using it ?
Is there any theme limitation ?