To draw upon Erwin Panofsky's schemata: a pre-iconological (i.e. "natural") account of the horse figure in William Kentridge's production of The Nose would do little more than identify it such.; the projection onstage would register with the viewer as a "certain object [known] from practical experience." That said, even this level of interpretation is complicated by the gestalt-effect which Kentridge employs throughout The Nose; figures coalesce and disintegrate as the vantage point shifts.
An iconographical or "conventional" analysis––which is, on some level, totally referential––affords more to consider. The operagoer aware of Kentridge's fascination with early filmic technology might compare the horse with Eadweard Muybridge's "Sallie Gardner at a Gallop," one of the earliest walk cycles (or "gallop cycles"). A classically-minded spectator, on the other hand, might observe the resemblance the horse-silhouette has to Don Quixote's steed, Rocinante. (Critics have gone further and tied this thread to Don Quixote's "Knight of the Mirrors" and his fake nose). Some might recall that Kentridge’s studies for The Nose included a video installation by the name of "I Am Not Me, the Horse is not Mine," some might recognize that name as a Russian turn of phrase, and others still might recognize the "form" (material) of the horse as cut-and-paste newsprint, an homage to the Russian avant-garde.
There are plenty of icons at play, then–– but an iconological interpretation would build from reference to synthesis. We might say that the question is no longer "what" ("primary") or "why" ("secondary"), but "so what?" Take the opera's introduction, for instance. An iconographical interpreter might be cheered to recognize the gestalt-converged face as Tchaikovsky's, knowing that he authored the opera. But why pay homage through such a bizarre mechanism? And what is to be made of how the "arrangement" turns further and becomes a horse? Iconography alone will not help the viewer recognize that revolution is a double entendre for Kentridge.
An iconological observer might contend that the horse itself is a point of convergence for not only different types of fragmentation (the animation and the collage––both being comprised of disparate images), but different media (the scenic bricolage w/r/t the fragmentary narrative of The Nose itself). It's only once these motifs are threaded together that we can get a sense for the underlying political valence of fragmentation in the horse and The Nose. Per Kentridge: "What history taught me was to understand the world as a process that continues to change with time through movements. Everything moves as the world keeps on moving. From this perspective, animation becomes a good metaphor for history."