Pros: The colored lines on the cats are nice. It's good that you added a variety of colors to the background. The cats are well drawn considering you were using a mouse. You didn't use Yellowfang's tail to cover up her paws, which shows you weren't being lazy with the picture, which is always a good thing. The orange sky is nicer than just a black/ blue sky. it could use hints of red and/ or pink to give it more color, but overall it's nice.
Cons: Yellowfang has yellow teeth, to start off. The teeth for her in this picture look white. Also, Brokentail's markings are darker .I would suppose that would make his facial features harder to see, but just a little darker wouldn't hurt. Also concerning Brokentail, his exposed skin shouldn't be as shiny. Two different shades of pink would be nice. And the skin doesn't need to be as bright, try making exposed skin a little more pale in the future. To add on, you forgot to shade him. That happens, to a lot of artists, so you shouldn't really worry about, much. Maybe you could edit the picture to fix it. Even though it's nice that you somewhat shaded the background instead of leaving it blank, It just looks like a bunch of scribbles. Try adding more detail to the background. It's just as important as the characters in a picture. For example, have vertical lines going in the direction of the grass or bumpy horizontal lines to show the texture on the dirt. Something that doesn't matter as much but I would like to bring up is that Fireheat should be watching from the cave entrance.
Remember, the only reason the "Cons" section is so large is because I'm explaining in detail what you need to fix, not necessarily that there are a lot of things wrong with the picture. You actually did a really nice job in creating a good picture. ^^
Pros: OK, i am no expert in cat art work, im not that good myself but i can say i love the style of your cats and there cute stubby-ness. Your eyes on them fits the right emotion for the pic and for using a mouse, you did AMAZING, i fail with mouses so congrats. The coloring is spot on for yellowfang along with her scars. Cons: The shading, it is good but it is also just a lot of lines witch add no texture to the earth, trees, and grass. Also On broken's skin you made fur marks on the tip and it's pretty long for a tail adding the base that you did for it. All in all i like it, good job and keep doin what your doin