I think all 3 look interesting. If i had to choose i would choose number 1 the ent stump. Maybe a nostalgic choice for me.
Btw. just to give you some overall feedback: i really like your tilesets. I like the alternative colors and the clean sprites.
The only thing bothering me is the border from land to water in zelda-style which looks the same in all 4 directions. Considering the perspective it looks off to me.
You already did a lot of biomes for your tilesets. Hard for me to think of something: i guess a snow/iceland would be interesting, or some cave-variations.