I don't know about ckvwm, but for rabidvwm I specifically make minimized windows show up on all desktops for some technical reason that I don't remember at the moment. You can't disable this because bad things happen, although I can't specifically tell you what at the moment. It might have been that it'd just take a lot more work and I wasn't feeling that ambitious... not that any of this necessarily matters if you're using ckvwm. :)