Though an odd thing to say about a scene containing a bunch of soot, I agree that the image is quite clean. In particular, the mousified baby, as you dub him, has an impressive sort of clarity about him.

The nice thing about this wall, is that it's unexpected. What I mean is, it's not as though this is a scene that people automatically think of from Spirited Away. So it has a nice way of reminding me of this and other less important, yet enjoyable details throughout the movie. Indeed, Miyazaki's world's boast an overabundance of imaginative characters. This wall reminds me off that.

Reminiscing aside, in a word, while nothing spectacular, this shot is just plain fun.

That said, what in the world happed to the other little guy, above the mouse? He is by far the worst part about this wall, and he ruins the entire thing! He does not fit into the piece at all. Rather, he does not sit into the piece at all. He feels too front, and too flat, as if someone stuck a sticker on top of your wallpaper. No matter how I look at it, he always sticks out, in a bad way, that says "something's not right about me." He needs to be pushed back into the picture, by being redrawn and/or reshaded. I think if you angled him more like the mouse, or angled him at all (instead of having him so straight on) and made the lighting on him more extreme, lighter on the right and darker on the left, then perhaps, he would fall back into the space of the scene.