It doesn't have to be perfect to be a beautiful take on the twins as they each enjoy Gravity Falls in their own ways. While Mabel is obviously more animated and playful as she tries to get the butterfly to land on her finger, Dipper shows a perfectly serious face. (Maybe he's re-reading about the crystals, judging by the small moose and eagle. ) But the real charm is that they look so comfortable together even though have very different interests and moods.
And even when it comes to technique you did a good job drawing the children and placing them in good perspective and proportion on that hilly grove. (Maybe some lines could use better evenness/symmetry, but small stuff. Also FYI, the kids have only four fingers on each hand (three plus thumb) while some of the main-character adults have five. Part of the spooooooky mystery I guess. Colors at the basic level and even "bulk" shading look pretty good to me, and I'm sure you'll be getting better blending on the skin tones, tree trunks, etc. every time you paint.
So very sweet work capturing a nice scene, a good say in the life for the Pines twins.
Yes, and thank you! I was worried no one would tell what they were--the creatures were a bit of a last-minute addition, so instead of just being minuscule, they're also especially poorly drawn. My initial plan was to have many fantastical creatures in the woods surrounding them, all of which the Pine twins would still be too pre-occupied to notice, but I gave up in the end and left it really, really simple.
Now that is a great picture. It's detailed, but not to the point where it detracts from the main appearance of the original stlye. Not only that, but the colors work together and are in perfect harmony in an organic sense.