The question about post-Columbian art was mine. Wouldn't it make sense that if there was art after we know the horse was there that there would be art before it? I was trying to get it through his thick skull that there is evidence supporting no horses. It's not just that we haven't found horse bones.
The problem is that the specific Mesoamerican cultures in question were largely "over" by the point that horses would have been introduced, in one way or the other. There were still groups of people descended from the former powerful culture, but by the time the horse would have been a presence (such as in mexico), the culture - including art - was under Spanish and Christian influence.
Given how late the horse became a presence anywhere near Mesoamerica (again, Mexico), the culture that would have been presenting works of art linking the horse to their particular mythology was long gone (or under the thumb of Christian Spaniards, hidden). But certainly the horse had a tremendous impact in Indian cultures in the regions where the horse spread successfully. This is the region I said would be part of the southwest region, and clearly the horse had a tremendous impact on those people. (see my earlier linked image)
If I understand your question, it's kind of like looking for pictorial representations of the automobile from the Romans. It just doesn't work, because they were gone by the time the automobile arrived.
The book "Horses through Time" states that mainly three areas of the New World provided the grasslands necessary for the spread of the horse - the plains of Venezuala and Colombia, the pampas of Argentina and Uruguay, and the prairies that stretch from Mexico to Canada. The closest to the Book of Mormon region is Mexico, and the closest time period would be the mid 1500's.
Part of the point about Mesoamerican art is that it reflects a religious ideology that relied on animal imagery. The later cultures in Mexico did share some of those traits, as do the later cultures within the US region, but I don't know how useful these later cultures would be in ascertaining whether the ancient mesoamericans, during the Book of Mormon time period, would have included the horse in their imagery. What is most useful, in my opinion, is to see whether their imagery included other powerful animals we know were around during that time period - and it does.
To me, the important thing to remember is that Mesoamerica art often revolved around religious ceremonies involving royalty, and their transformation to their mystical animal companions. So Book of Mormon apologists insist that the horse was perhaps very limited in number (and that's why we can't find any bones), and associated only with royalty. But that argument makes it
more likely that the horse would be included in those very images of royalty and their animal companions. Their argument is like saying the King is associated with a certain crown, but we shouldn't expect to see that crown in the art depicting the king.