"In the goblin lair lives a goblin king," reads the goblin entry in the Moldvay monster section. I like the phrase; it's got a pleasant meter to it that lends some appropriate fairy-tale whimsy.
Goblin kings are, per the rules, 3 HD creatures (with 15 hp) that get a +1 damage bonus and a 2d6 squad of 2 HD goblin bodyguards. Tolkien already did the generic "goblin, but bigger" goblin king in the distant 1900s so we should be emboldened to leave that sinkhole of creativity and journey forth into newer realms of possibility. Here are some alternative "kings:"
- A huge, tumorous maggot. The goblins prevented it from pupating, and instead feed it non-stop in long ant-like assembly line so that it just grows, and grows, and grows.
- A David-Bowie-looking elf with a magic crystal ball. He likes mischief and singing songs about being mean (or something, I don’t know, I've never seen the movie).
- An unsettling avian puppet effigy. Made of wood, feathers, and guano. It's piloted like a mech by a team of goblins, who inexplicably work in such perfect sync that the effigy seems alive. If any of the pilots die, other goblins will hurriedly climb into the wood frame skeleton and take their place.
- A giant goblin toddler, about the size of a full-grown cow. It’s all the goblins can do to keep him fed and entertained, for they fear nothing more than his tantrums.
- An ancient corpse desiccated beyond recognition. Its limbs are long and bone-thin, and its face is just blue-black skin stretched over an eyeless skull. It’s shamanic bodyguards claim to be the interpreters of its strange decrees, which are delivered in the low groans that occasionally escape its mouth.
- A captured, half-crazed adventurer. One night he was just getting settled into his bedroll, but the next thing he knows he’s chained to the throne somewhere deep in the goblin warrens. The goblins worship yet always humorously misinterpret his commands. Many failed escape attempts have left him frazzled and desperate.
- A tall, beautiful, exquisitely muscled paragon of goblinhood. Unfortunately, not much more intelligent than a typical goblin.
- A haggard wizard who fancied at one time that he should vat-grow his own horde of goblins. He realized only too late, of course, that goblins are much more trouble than they’re worth, but he just can't seem to get rid of them. Spells known: Charm person (goblin), Ventriloquism, Mirror Image.
- A grim, sinister warrior covered in terrifying armor. He calls himself “The Overlord.” He's got all the trappings of your generic grimdork villain: glowing eyes, booming voice, preternatural hatred of insolence. The goblins are scared out of their mind by him but he’s no tougher than a 3HD fighter.
- Looks like a goblin, sounds like a goblin, acts like a goblin, but... it’s definitely not a goblin. Whatever it is, it looks to be wearing an ill-fitting goblin suit: The skin sits too slack in some areas and too tight in others, weird bits of hair peek out from frayed seams, and the face doesn’t move as much as it should when it speaks. Very conspicuous to anyone who sees it, but the goblins have no idea it isn’t one of them.