Seriously, though, what is one to make about these choices of subject matter? Of course paintings, animals, and mythology are all outside the self. Of course they are all, you know lingua francae of certain sets of people -- heck, we all have pets; heck, if we went to a decent college we'll know the story of Hecuba; double-heck, we'll know about chalk drawings of Rembrandt (probably got that wrong).
I don't want to put a trademark on what inspires, or a poet's method, and especially execution. I do want to make this observation -- this desire, particularly American poets, to make a connection with a subject matter at least as equal to this vision of poetry as immortal, as if by piggybacking on the mythical or a domesticated animal or the Met's permanent collection, the poem will last longer than the sentiments and, God forbid, the self of the poem or the feeling of the poem show through, through a self the poem creates. I added that last phrase for those who believe the poem is not a reflection of self but a reflection of words. I happen to believe the words of course come first, but these words are not random, the ghost in William Carlos Williams' machine is the poet. Look at me, upbraiding Williams! But I think Williams had his agenda, and I have mine. And believe me, this choice of subject matter thing, I've done it -- my BAP poem talks about a painting, Frank O'Hara, Cavafy. (And that's precisely why my mom doesn't understand it -- she doesn't read widely, didn't go to college. A trucker's ex-wife, really.)
I'm sort of dancing around my point here, which is what blogs are for. My point, I think, is that poets are usually of such a social station -- or perhaps more accurately, emulate a certain social station -- that paintings, animals, and mythology is the only palette we're handed, by both the poems we've read in, oh, the last desiccated half-century, by the professors we look to as mentors, and by the vision of what a poem is, what is to happen in on, and what a poet is, and what a poet is supposed to make happen.