If your asking for a design idea, I would love to see something based on a sound amplifier. It would totally be a cool bulky electric type :D
As long as it works well in a double battle alongside Loudred, I'm fine with this.
Take a look at what kinds of environments are in your region, and make Pokémon that would live in those environments. Ruby/Sapphire had a volcano, so we got volcanic Pokémon like Torkoal and Camerupt. Black/White had a big, modern city, so we got some city-dwelling Pokémon like Trubbish and Garbodor. So if your region has, say, a jungle, you'll want stuff like snake Pokémon or parrot Pokémon.
If you're going to include any of the original Pokémon, then think of animals/plants/objects that haven't had Pokémon based around them yet (or you don't like the ones that are), and work with that. For example, a dolphin Pokémon, or a giraffe Pokémon better than Girafarig (no offense to Girafarig fans!).
If your game is only going to have new Pokémon (like Black/White did), you don't really need to do that - since Meowth and Growlithe aren't going to be in a game, people won't complain if you make new cat and dog Pokémon.
Finally, try not to have too many similar Pokémon. Mix up the body types; have a bunch of four-legged mammals, a few insects, some reptiles, some birds, and a couple of humanoids (as well as anything else you can think of). The more variety, the better.
Maybe it would be good to have a Pokémon creation guide for all those games/hacks with fakemon... Any fakemon designers want to help with writing one?
