Ok, I tried experimenting with more of a leafy texture w/ @DXimenes' advice (I didn't want to go as detailed as his piece because I didn't think it fit the overall game's style of simplicity) and with @Moth's suggestion to look at Zelda for guidance.
#1 is the original
#2 is the first pine tree I tried to fix up and add leafy textures to
#3 is my attempt at cleaning up some details in 2, but I may have gone too far?
#4 is reverting back to #1's lineart after some people on reddit suggested that #2 and #3 had weird perspectives
#5 modifies some of the perspective to be more consistent... I think?
Which one do you prefer?
I understand that you guys want me to switch some of the colors, but every time I try to swap some of the colors for others, it ends up looking wayyy too saturated for some reason. I already do some hue shifting, so if you guys could give me some more advice on that front I'd really appreciate it
I think they look pretty good, but maybe they could use some shadows around the trunks like the trees in A Link to the Past?
As Aamp suggested you might try adding a bit of shadow to it (also added a strand of grass overlapping the rock- a deceptively tricky proposition because you want to make sure the strand is identifiable as grass and not a graphic error, and you also don't want to take away the personality of the rock):
The issue with adding shadows/preset grass into the graphic is that our trees can be placed on any type of terrain in the game-- The player has the option to place the trees/rocks on dirt or snow if they wanted to. I've tried adding some alpha'd shadows, but when the trees were planted near each other it caused shadows to overlap and make the graphic not work out at all.
In the end we might end up doing a fix in the game engine, but meh... if you guys have any other suggestions I'd love to hear them.