I'm aware of the problem, too..... and have told Vern about it, about a year ago:

Unfortunately not all decorative sprites have a checkbox for "Foreground".... which is often a real nuisance. It was even worse in the Exp.Pack...where - gladly - Vern has put a few more in, after I complained about it. But there are still enough things that could need such a checkbox..... 'cause, as you say, it doesn't help at all if you place them in layer-6....they're still in the background....until they have such a checkbox, of course.