A Portrait Ghost, Neville, disguising a portrait, while waiting for the anime teenagers to spot that portrait, and then, attack them.
A Portrait Ghost is a type of ghost that was once a portrait in a Nintendo Gamecube game, Luigi's Mansion.
They are also the rarest type of ghosts found in real life. Despite how that game portray them, they are NOT aggressive enough to scare people or haunt places, but are peaceful and gentle creatures, plus they are very peaceful entities that won't effect living beings, and since they are immortal, they don't need to feed, drink, sleep, etc. Unlike in that game, they don't disappear/vanish completely in sunlight nor they stay the same place for the rest of their lives, so they won't be restricted to the place where they died.
They are well known for their transformation into portraits as a stealthiily move in case of attacks, or when a mortal is coming. Their portraits came in different frames. They turn into bronze frames, silver frames, and then gold frames, then start the cycle again.