background-image support for transitions and animations

Hello,

This is the first time I'm mailing the www-style list.
I was wondering if the background-image property is supposed to be supported
by css transitions and animations?
This doesn't seem to be supported, I've tested this on webkit. (chrome 13
and safari on iPad)
I'm asking because it's very common to create slideshows of images that fade
from one into another.
It can also create a nice hover effect.
Currently, this is done by placing one image over another and fade the
opacity.
This requires two elements.
Three elements are required when there's also foreground content.

My question: is this planned standard behavior?

Regards,
Michiel