This is excellent, thank you @Chip-Valecek and @TessW I'll be looking into color saturation over my weekend and I'll see about adjusting this piece in particular. And as for Eye shading, I definitely would have but I totally forgot so I'll touch that up when I attempt to saturate colors.
@Chip-Valecek I see what you're saying about the lineweight, that is one of those things I have to be thinking about otherwise I am totally oblivious to it. My pen/Tablet is pressure sensitive so some of them on the inside of say the tree may come out thin but if they are one stroke they tend to be the same thickness, as the robot is. But I can see where they can be thinner.
I originally drew this in ink for Inktober last year and I liked it so much that I decided to draw and paint it digitally. My parents were in town for the last three weeks, so I have not had time to post anything. In the meantime, I have completely forgotten how to post in the Illustrations subcategory, as I can't remember how I did it the first time!
I think this piece is so lovely, and most of my thoughts have been covered already.
Another thing you might try and see how you like them is to add a bit of bounce light on the tree and girl and dog to add even more contracts to them.
I also thought maybe you could give us something of interest towards the bottom of the screen that adds to the story- right now everything interesting happens in the upper 1/3 of the image and there's nothing else to really lead us around the rest of that space, other than your lovely painting. (Very slap-dash) thoughts I had were low-contrast fireflies, a dark cat climbing the ladder, a sign tacked to the lower left tree that says "no boys allowed" or something like that, a few lizards or mice climbing up the ladder, more bats.
Alternatively, if you want her to be the center of the image and for the scene to feel serene, solid and strong, you could bring the action down more toward the center of the page, or extend the painting up a bit further.