Maybe make a fantasy horror adventure multiplayer game.
I'm just kidding, scrap the multiplayer, that's too hard for RPG Maker, but the rest of them should be achievable.
Have you considered a horror game? Just create some maps with a chain of puzzles, and slap on a slightly restrictive lighting system, ambient background noise, blood splatters appearing on the walls when you step on certain choke points, and you've got yourself a horror game.