Gem Hunters: Xenogenous Predicament

It's pretty hard to do good random nature scenes without actually doing full 3D terrain generation even for a 2D isometric map, otherwise it looks like a flat land with someone randomly doodling tiny spots of other tiles.

Something like this, just not as gigantic:
http://rpgmaker.net/games/5016/blog/10677/

You can then use the PRM method to generate and connect POIs to fill the map with events, locations, people, etc. and generate a progression for them easily:
https://en.wikipedia.org/wiki/Probabilistic_roadmap
http://people.cs.uu.nl/roland/pdf/compare.pdf