Think back to when you studied the 10 Commandments. You shall have no other gods before me. To worship the devil would mean having something more important than God , and Jesus knew that was wrong. It is still wrong today, but there are many temptations in the world to worship other things. Maybe not worship in the sense of praying to them like God or going to church to worship them, but worshipping them by giving them priority in your life - making them more important than God.
Kids do most anything to collect more and to get the special ones.
Decide on a title for your poster that will help people who see it know that these are things that we should not worship. We should worship God. Have someone write the title on your poster board. Arrange the pictures on the poster board and glue on. The Hebrew Scriptures just like the devil did.