Can target and source in a visual or multimodal metaphor be reversed? No, they can't!
What is it about?
It is generally accepted that the target and the source in a verbal metaphors are not, in a given context, reversible. For instance, in a given situation one cannot simply reverse "my surgeon is a butcher" into "my butcher is a surgeon" (of course in a quite different context "my butcher is a surgeon" may be a viable metaphor). Even though visuals don't have a grammar (which helps in assessing target and source in many verbal metaphors), pictorial/visual metaphors also do NOT allow the two terms to be reversed. In this respect, though not in others, Carroll's (1994, 1996) proposals concerning the nature and identifiability of pictorial metaphors are wrong. Carroll also is wrong, in my view (see Forceville 1996) that prototypical visual/pictorial metaphors are of the "homospatially noncompossible" variety -- that is, what Forceville 1996 labels the MP2 (or: hybrid) subtype. This is just one type among others. Finally, the paper makes suggestions for how metaphor theory needs to be adapted to account for cinematic metaphors in which music and sound play a role.
Why is it important?
There not that many criteria that help an analyst identify a visual (or multimodal) metaphor, and the irreversibility of target and source is one of the few. If one rejects this criterion by claiming that (some) metaphors allow for this, this catastrophically broadens what is to be considered a metaphor -- irrespective of medium.