Quick an short
The landscape in Istaria looks in most areas like painted, because theres no "enviromental interaction" like clientside calculated animals that walk around.
But the biggest part of this painted feeling take in the inflexible trees.
They stand there like painted and bring over this feeling to the player.
How would it be to redesign the tree models so the are moving a little in an imginated wind.
Such tree models don't eat up too many ressources and maybe they could be addet that way, that players can say by system-adjustment if they want to see the old inflexible models or the other ones.
There a already existing so nice models from bionatics.com that would fit into istaria with some rework. The existing plugins for Maya and 3DS would make it easy to implement thm into our world.