A mondegreen is the mishearing of lyrics resulting in a new meaning. Read the linked Wikipedia article for examples.
What I'd like to propose here is the term forced mondegreen for those cases where an image or images are shown along with a song to force (or at least encourage) a particular mishearing.
In both cases, a mondegreen was possible but the visual context the song was placed in forced the mondegreen (at least if you didn't know the song before).
Now that I've come up with a term for it, I'll be on the look out for more examples :-)
It occurs to me this is all a classic example of priming in psychology.