(This is my attempt to spark some serious discussion. I'd be grateful if certain people would refrain from trolling and give a serious answer for a change. I know you can do it, guys! ;) )
So what do you guys think will the new places Luffy & crew will sail to look like? We already had: "ordinary" climate, snow, a desert, the sky, under water, jungle, a graveyard and Water 7.
Personally I'd love to see some kind of Phantom Island that appears only every so and so many years. The SHs would have to get off before it disappears again, otherwise they'd be stuck there for an unknown amount of time. Maybe there's some old civilization on it that hasn't yet realized how time has passed.
Or Elbaf maybe? It was never stated where exactly it is. It could be the in the New World, couldn't it? A viking themed island sounds good to me.
A Poisonous Swamp Island? I image that to be rather colorful. The problem is that it's impossible to breathe because of all the poison in the air so you need special equipment.
Or an island that looks like a simple rock with nothing on it but it's actually a Cave Island.
Now, I know this is somewhat kitschy and overused, but a Steampunk kind of place would be awesome.
And... an island made of candy!! xD