He can't really do that though, because the paintings are merely a moving image that happens to have the ability to speak, they can't really make any decisions they didn't already make in life. He could talk to Dumbledore's painting, but the painting can't really help him

Also I think Rowling may be expanding the series, there's still four or so Horcruxes left, and it's going to take a while to figure out where the heck they are. We know what most of them are, yes, but where they are is still to be determined.