Thanks Paul for getting in contact with me.
I’ve just looked at the issue you describe and can confirm this is an undocumented bug in IE8. For this reason, I’ve documented it and created a [URL=“http://jhop.me/tests/bugs/ie8/background-image_first-child.html”]reduced test case.
Unfortunately, I’m unable to create a bug ticket at Connect since Microsoft has decided to recently close ticket submissions until they have transferred all open tickets to the new platform for IE9. I will, however, remember to create a ticket when they’ve done this