would love to know the best place to post art.
It all depends on which type of art you're referring to here, if it's all about bitcoin art works then it's welcome on the forum's Meta, beginners and help or bitcoin discussion boards, but if the purpose of your art is to advertise your business or organization then you need to use the service announcement board for doing that.
There's no board specifically assigned to that.
There may not be a dedicated place for arts but just as being said earlier, you need to define the purpose of your art with the content before finding a suitable board it may fit in.
Every off topic or threads posted on the wrong board ended up here, but i can tell you that we've got alot of art contest thread nit ended up being on off topic because they were always on point.