Two things to watch out for in the future:
1) You're probably using one too many shades of each color. The darkest shade of blue is almost invisible at 1x; I don't think you need the lightest shade of green either, and you definitely don't need the almost subconsciously tiny variation in shading on the lips.
2) There's a lot of banding going on here. (That's when rows of pixels line up perfectly with the outlines they're next to, most obviously on the lips.) This is making the image look flat and jagged in a way that should be avoided.
But I think you're on the right track elsewhere - as with the folds under the eyes and the shading on the "snout", which both look great. (And in other pieces you've uploaded recently, which either don't have these issues or have them in trace amounts that are almost negligible.)
Will try to fix those details and pay more atention in the future! Thx!!