This is not at all an irrelevant analogy. True, a painting belongs to a different category than human beings, but human beings belong to a different category than God. The difference between God and men is far greater than the difference between a man and a painting. The difference is infinite in all respects. God transcends all categories.
A human being is an ultimate end in one sense but not in another. Yet even earthly human life is not an ultimate end, since the taking of human life is often justifiable. In fact, individual lives can be sacrificed for the common good, as in the case of war. Ultimately, eternal life with God is the end that human life is directed toward.