Yes, you can use Agnus Day cartoons for free in your bulletin, with acknowledgment, and they are linked to the RCL as well:
Snippets originally from:
2005-03-18 — Poor Thomas…He’s makes one mistake and it blows his whole reputation.
A week later his disciples were again in the house, and Thomas was with them. Although the doors were shut, Jesus came and stood among them and said, “Peace be with you.” Then he said to Thomas, “Put your finger here and see my hands. Reach out your hand and put it in my side. Do not doubt but believe.” Thomas answered him, “My Lord and my God!” Jesus said to him, “Have you believed because you have seen me? Blessed are those who have not seen and yet have come to believe.” Now Jesus did many other signs in the presence of his disciples, which are not written in this book. But these are written so that you may come to believe that Jesus is the Messiah, the Son of God, and that through believing you may have life in his name.— Second Sunday of Easter, Series A