One thing that I appreciated greatly about Galactic Civ 2 was the interesting variety of planets that emmerged from the randomized special tiles that you would find on them. I would personally like to see the return of such a concept in elemental with these tiles speckling the whole of the landscape (rather simply from planet to planet). Sure, there can be large resources like iron, shards, gold etc., but there could also be a host of other special tiles that enhance other elements of city growth. Some tiles may also not be revealed unless you have certain tech pre-requisites. Some examples might be:
Fertile Highground: If you place a windmill on this tile, it also acts as a small farm as well.
Solid Ground: This tile gives any housing built on this tile a 50 percent bonus.
Fertile Pasture: Any ranch built on this tile yields 50 percent more livestock.
Ley Line Nexus: If one of your wizard towers is built on this tile, it gives the tower a 200 percent research bonus in addition to a 50 percent increase in range of your global spells.
Mushroom Field: Any mine built upon this tile also yields X food.
Ancient, Underground Library: This tile grants a 300 percent research.
Ancient, Underground Forge: Any weaponsmith built on this tile will yield +1 to calibur weapons and armor as well as an increase in production speed of weapons and armor.
In this spirit, certain roving monsters, barbarians, or dungeons creatures might gravitate toward these locations if they have something to gain from it (trogs to Mushroom Fields, hunting trolls to pasture lands, liches to Underground Libraries.)