The GFI Skeleton Dogs (MIF25921805) are how I picture Hell Hounds to appear, which is not surprising, since they are the old Dungeon Dwellers Hell Hounds (Heritage 1264). They probably aren't considered particularly good sculpts by today's standards, but there is a certain charm about them that I don't find present in modern miniatures. But then again, if you stare at them long enough, they seem to somewhat resemble emaciated cattle...
Relatives of the Hell Hound can also be found in classical mythology and fiction. Two examples are shown below.
First we have Cerberus from the Fantasy Lords Monsters of Mythology boxed set (Grenadier 6004). Then there is a Hound of Tindalos from the Call of Cthulhu Creatures boxed set (Grenadier 6502). This particular miniature has been re-released by Mirliton as Bloodsniffers of Chaos (CH015) under their Fantasy line.
Prior to painting Cerberus, I looked to ancient Greek vases for guidance on his coloration, and found several choices.
I opted for black, with a concession to tricolor around his throats.
Finally, we have the lineup for all three breeds. They are all really big for dogs, but quite alright for monsters.