Paul is alluding to his preaching and not to any kind of pictures. When he proclaimed Jesus Christ in their presence, he taught them about the meaning of his crucifixion1 and the implications for their Christian lives.2 Elsewhere in his letters Paul uses the term crucifixion
as shorthand for the gospel message (1 Corinthians 1:23; 1 Corinthians 2:2).
1 O foolish Galatians! Who has bewitched you? It was before your eyes that Jesus Christ was publicly portrayed as crucified.