Hobgoblins should in essence look like humans with goblin heads. They should not be big and brutish like a bugbear or an orc, nor should they be small and frail like a goblin. They should also have a skin complexion ranging from orange to reddish-brown.
Having checked the NWVault it unfortunately doesn't look like there are good custom models for hobgoblins like there are for bugbears.
Personally I think it would be best to keep using the normal hobgoblin model from NWN1 until there are better and more accurate models on the NWvault.
This is what a hobgoblin looks like in 4e, which I think is personally the best depiction, since it has a distinct appearance that can't be too easily confused with any other creature.
