Hey @Xiaogabe, looking great so far! Since you requested paintovers I gave it a shot!
Disclaimer: this may not actually be good advice :)
Here's what I changed:
Threw down a quick perspective grid with Carapace. You obviously were headed toward a "looking up" perspective so I made the verticals converge above the frame. From the columns on the shrine it looked like you were doing a one point perspective, but the height difference between the cloaked statues was more two point (assuming they're lined up parallel to the shrine). I went with the 2-point and massaged the shrine to fit that perspective. I think the 2 point works OK because it makes the shrine "look back" at the main character so there's a bit of "flow" in the image.
From there I copy-paste-transformed the left statue, the main character, the horse character, and the lion pillar to fit the new vertical perspective lines. I realized afterwards that the arches were supposed to be a fence/wall connected to the lion pillar, but I pushed the into the BG because I thought they were aqueducts. So, ignore that part :)
You mentioned that you're already trying to add more overlap so I just tried to fill in the empty space with overlapping stuff - trees, branches, etc. You can see I added some behind the lion pillar, (then another behind that one), some branches behind the left statue, added more roots from the big tree so they can reach the left statue and go behind it, and I added some bushes/vegetation around the base of the statues. The last thing I added was another foreground tree as by that point the right of the image was feeling sparse compared to the rest and my eye kept escaping out of that side.
I added some slight detail to the shrine since it's a focal point (this detail would eventually need to be bit sharper/better I think), and bumped up the contrast of the shrine. I also bumped up the contrast of the path to the shrine (really I just made it lighter).
I darkened the lion pillar a bit to pull it forward from the branches behind it, and added a bit of lighter values behind the horse's head to keep it from blending into the BG.
I brushed over most of the image with just a hint of darker values, EXCEPT the shine, so that it would have the lightest values in the image. Probably I could have pushed this a bit more too. Then I further darkened up the 2 foreground trees to pull them forward a bit more. Finally I added a bit of white behind the main character to pop it out from the BG even more.
Although I didn't push the big tree far enough really, I think it could be a bit darker and of course more detailed, since it's the real "star" of the image.
I think my separation between the overlapped layers (making sure each overlapped layer is different enough in value at the places where they intersect) could be improved a lot, but hopefully this gets the idea across!
That's it I think, I hope this is an improvement and that you find it helpful!