Kukkonen, Karin. 2008. Beyond Language: Metaphor and Metonymy in Comics Storytelling. English Language Notes 46 (2):89-98.
This paper from the literature point of view explores meaning-making in comics, particularly from metonymy and metaphor. It argues that the "semiotic" approaches of European comics scholarship that dissect parts into structrualist "minimal units" are insufficient to capture the complexity of comics' meanings, and is thereby a tacit argument against viewing "comics as a language" in the semiotic sense.
(Groensteen takes this same perspective against minimal units, though maintains the "comics as a language equation. I actually think that "minimal units" are *kind of* there, but it's beside the point, since linguistics hasn't really been concerned about "minimal units" since around the 1950s...)
While she does explain and support the cognitive linguistics view of metaphor taken from Lakoff and Turner, she does not actually use it in exposition. Most of the examples of metaphor and metonymy she cites are through a close reading of Watchmen, involving large scale metaphors on the scale of plots, themes, and motifs, and doesn't ever cite the correspondences of one "coneptual domain to another" that conceptual metaphor entails.
Her view of metonymy is equally broad. For part-whole metonymy she cites scenes where a whole understanding of an environment is given across multiple panels. This would imply that all instances where multiple characters are shown in their own panels but part of the same broader environment (what I call "Environmental-Conjunction") are metonymic, because they construct a broader whole by only seeing the parts. This is a curious proposition that I (mostly) like, though one that seems at least partially limited by not having a robust view on the broader narrative grammar for how sequential images are comprehended.