You mean with the BenchTrash app? I don't run it personally but from what I recall, doesn't it allow you to select "full" and "empty" icon images through tooltypes? Or does it pull from the def_icons? I'd have to load it up and check.
Also, if you're not running the latest Boing Bag 4 you might check on Aminet - I think there's an updated version available.
Edit: here you go:
http://aminet.net/package/util/wb/BenchTrash
