Representation was not invented by Descartes, as Brandom tends to suggest. Concepts of representation had wide currency in the middle ages. The word used was literally repraesentatio.
For instance, Duns Scotus wanted to rewrite Aristotle by insisting that there is a single meaning for “being” that underlies all the different meanings Aristotle had distinguished. The underlying minimal definition of being he proposed was precisely representability. Olivier Boulnois documents how Scotus believed he had invented a unified ontology that Aristotle thought was impossible, and did so on the basis of a doctrine of being as pure representability. Scotus thus appears as an arch-representationalist. Whatever else one may say about it, his notion of representation is clearly not the same as resemblance. Every medieval university had a Scotist on the faculty.
If memory serves, Aquinas had a doctrine of the possibility of perfect representation. Since it is perfect, this cannot be reducible to mere resemblance. Perfect representation is effectively equivalent to a kind of immediacy.
Some contemporary scholars also translate Greek Stoic phantasma as “representation”, based on the functional role it plays in the Stoic system. The Stoic theory in question dealt with sense perception, and was part physiological and part epistemological. It purported to provide a foundation for immediate certain knowledge of represented objects from their mental representations in perception. This sounds like representation before inference, and also like another variant of putatively perfect representation, which therefore would again not be reducible to resemblance, and would again be effectively equivalent to immediacy.