IC Düsseldorf lets you choose:
Booking Superior Room -> Upgrade to King Club Intercontinental WITH Club Access OR Upgrade to Executive Room.
If you book Club then you will get an Upgrade to Executive Suite.
According to this
http://www.flyertalk.com/forum/18318727-post5343.html
it seems that if you include breakfast in your reservation the Upgrade will be to Executive Suite anyway + Club Access (from Superior Room).