Sir Lawrence Alma-Tadema painted An Art Lover in 1868.
To my eye, the work is a thinly veiled excuse for Alma-Tadema to indulge (and show off) his love of classical art. As such, many elements of the painting are clearly based on known pieces of classical art.
Perhaps my favorite, though, is the work in the very back. Behind a pillar, it looks just like the Alexander Mosaic.
But the mosaic should be on the floor, not hung up on the wall. Now, in 1868 it was on view on the wall of a museum in Naples, so perhaps Alma-Tadema just didn’t think to reorient it into its original position.
I prefer to think, however, that Alma-Tadema understood perfectly well. After all, the mosaic is generally considered to be a copy of a much older painting—a painting, which would be on the wall.