To start, the Charmander is simply adorable. The black strokes are particularly well-used in this one, defining its form nicely and artistically without being overdone. The shading is effective and has personality.
Additionally, I think this one has the best backdrop of the three you've done so far. The golden yellow-browns are appealing in combination with Charmander's orange, but they don't distract from the Pokemon. Overall, they establish a feeling of warmth that is perfect for a fire-type, but without any sense of destructiveness or uncomfortable heat. The grass blades came out just perfect, too. <3