All adventures have to start somewhere, right? The map or location is key to setting up the mood and largely determines what you might encounter. What would your ideal map (or maps) be like??
Flat and plainlike? Rigid and mountainous?? Both??
How about the number of actual biomes?
What kind of towns/cities/etc. would be in it, and would they all be similar or drastically different?
I think it depends on the scale of the RPG, but areas with different themes are a must. We can’t just have a game where only a mountain exists, and thus ends up maze-like out of player confusion.
A good example of a small-scale but varied map is the SFRPG. It’s mostly the one city, but there are clearly different districts and styles of locations ranging from swamp to donut shop.
Since my strength is more programming I tent to stay away from directly designing maps. Instead I tend to use procedural generation for creating maps/dungeons. I find that not only is it allowing me to play to my strength it can really help increase the amount of content I can give to users without a ton of work.
FATE is a good example of what I try to do for the most part.
I’d say the only ideal I could impart for any game, regardless of structure or genre (for the most part, anyway), is to maintain distinctiveness. Every scene should look and feel different from each other. Unless you’ve got a big sandbox to fill, take your time to make each piece special in some way, be it a secret item to find, a unique NPC, or an interesting setpiece.