I don't know that I still do, because I'm just so weary these days (years), but I used to find meaning in visual art. The thing I found comforting about it is that unlike other more abstract disciplines (like philosophy, for instance, or even literature), the meaning of a work of art is in its physical presence. It's right in front of you. I went to art school, so perhaps visual art is easier for me to understand than it might be for someone who hasn't studied it, but I find that it explains itself, and at its best it just "is."
I don't know if this has anything to do with AS, but I suspect that it does. Concrete objects might have more meaning for me than abstract ideas.
I'm not sure if this is of any help as to your original question. I don't know if your son could find that art is meaningful to him or not, if he were to get to know it.