i like this one the most, cuz this type of art doesnt use shadows or fur patern mostly.
could be a little bit darker though, i can barely see his paw front his belly

nice piece of work ^^

When I shade a picture I usually use a slightly brighter color than usual combined with the shadow color. The shadow makes the whole pictures seem darker and the 'bright' color seem a bit darker as well. Though, sometimes if you use a color too dark you end up making the color look too 'bright' if you know what I mean... Also, the shading would outline the paw as there are no lines in the pic =P

Gotta love illustrator, i like this one as well