I agree that the frame really adds a final touch to the picture that I don't think it would have on it's own. I like the warmth of the colors you've used, it works to pull the artwork together in a tight way, and conveys the exotic setting, especially with the silhouetted hanging vines.
One thing specifically the really struck me is that you do a great job of setting up the dual conflict between the two characters by having them each take up one half of the picture, but then having the cobra on Riki's side too as almost scenery, and it definitely kind of heightens the drama and danger of the mongoose taking on this giant cobra, along with your use of expression on the animals in their faces and their demeanor. Even though you draw them both very realistically, their expressions are very clear and almost human, but without seeming cartoonish.
The style you've used for this picture is so simple and colorful and I love the white detailing you added in afterwords. I think it perfectly captures the folktale- meets- storybook vibe of "Jungle Book".