Andrew has no photos. Technology was never his strong point, even the simplest of cameras, and he knows they would have been lost with Sunnydale anyway.
He remembers his dead as best he can. He never saw Warren's body, since it was destroyed before he even knew Warren was dead, and he's glad of it. Jonathan, he killed, and that image he'll never forget. And Anya died for him, so he all but killed her too.
He wishes he had photos of the three he mourns. If he did, they might replace the images, real and imagined, of their bodies.