The Historical Lineage
The canonical Western memorial dog painting is Edwin Landseer's The Old Shepherd's Chief Mourner (1837).
The painting depicts a sheepdog resting his head on the closed wooden coffin of his master, in a sparse stone-floored interior. There is no human figure in the room. The dog's expression is not grief in any theatrical sense. It is presence — the dog still where he had always been, with the person he had always been with, regardless of whether the person was now there to be with.
It was an enormous popular success. The work entered museum collections, was reproduced in countless 19th-century parlors, and established the visual conventions for the dog memorial portrait that have lasted to the present.
The conventions: quiet domestic interior. Soft directional light. The dog rendered with weight equal to a human portrait subject. No sentimentality forced into the composition — the gravity comes from the situation, not from the painter's adornment of it.
The studio behind dogoilpaintings.com works in the same register. The conventions are unchanged. The production has moved on.