I like exploring oversized human houses in games. Obviously this couldn't work with Banjo-Kazooie becuase they are similar size to humans so everything would be regular size. But Chameleon and Bats are very small so id love to explore an oversized house in a "rare" game. Climbing up tv units, finding a way up onto the kitchen counter, entering the plumbing, stealthily avoiding humans, swinging from lampshades etc. Sounds fun.
As for classic themes. Snow world amd jungle world are a given.
Lava world i could do without.
Horror world would be cool if done properly.
Unrealistic Mario worlds (made of cake for example) i hope to see NONE of.