The Primary theme for the month of May is the 4th Article of Faith: "We believe that the first principles & ordinances of the Gospel are: first, faith in the Lord Jesus Christ; second, repentance; third, baptism by immersion for the remission of sins; fourth, laying on of hands for the gift of the Holy Ghost."
You can get the free printable for May {here}. It's sized to be printed as an 11x14 picture.