Usually there is a person or two at each table who isn’t totally engaged in listening to questions and discussing answers at any given time. It’s a good idea to have some tasks they can fill up their spare moments with.
For example you can announce at the beginning of the evening that there is a prize for the best decorated answer sheet. Any people not actively involved writing down answers can take some time out to scribble down some drawings.
Or perhaps you could distribute an extra blank piece of paper to each team table and announce that at the end of the night there will be a prize for the best drawing of Elvis/The Earth/The Mona Lisa etc.
Of course you will need to look through all of the attempts and come up with a winner which will mean a little more work for you. You could quickly scan the pictures, select the top three and then take them around the room and ask everyone to vote with a show of hands which one they prefer.