It is not required that you tip the furniture delivery people, and sometimes it is against policy for them to accept it.
However, if you feel that they were particularly helpful, possibly putting the furniture in the place you wanted it (instead of just leaving it in the middle of the living room), it is nice to provide the offer of a tip for their assistance. Some will take garden equipment it, some will not, but atleast you showed that you were happy and appreciative of their work.
If you do not give a tip (or they are not able/willing to accept), but you are still satisfied with the delivery, note their name(s),call the store, ask to speak energy suppliers to the manager of that department and tell them what a great job they did. That is often better for an employee than a few bucks!!!