Wow, you've got skills! Lovely piece!
Over all, I think my biggest critique is that this feels like a bit of a tease. You've presented it as a character design with the simple background, but you've introduced such strong story telling elements with it's pose, gaze, and expression, that it feels like a bit of a let down not to have more of the story presented. At least a hint of an environment and other clues to what is in store for this mouse. If you had made the pose/expression more nuetral, then the simple background makes more sense for me.
For a nit-picky technical critique- I would agree that the basket weaving on the saddle is slightly distracting. It, along with the leg on the right, is demanding a lot of visual attention. I'd suggest lowering the contrast on it slightly. Perhaps adding a bit of shading to the overall form of it, making it more clear if it's concave or convex and perhaps lightening the values of it's deep shadows just slightly. You might also consider lowering the contrast of that right leg sticking out of the silhouette a little as well.
Just a couple of thoughts! Again, it's a lovely piece that shows off your skills very nicely. I would love to see it in some sort of environment with more story telling elements- it would be an even bigger treat for your audience!