This image is nice but you might want to try toning down your colouring, its very garish! Try to look at the way real life things are shaded and use this in your artwork to make it more realistic. The hair however looks nice, but the plait is sticking out at an odd angle, maybe you should have drawn it hanging down the way gravity would force it to go IRL. The only other major thing that stands out with the image except for the colouring is the eyes. For female characters try not to give them such dark and thick eyebrows and use a little less highlighting around the eyelash area. You might want to try experimenting with line thickness all over the image to give it a more 3D feel too.

The character design itself is very interesting and she makes a cute character. I'm not sure many ninja mice fems exist in the furry fandom!