Ok I took the time to make a major edit, just because I like this so much and I feel you could improve in a few areas.
Time to break out of your comfort zone!
I think the whole thing iss too outliney and the selout all over the place breaks things into little solitary cardboard cutouts, I feel as if i can take the whole treestrunk out of the picture leaving a hole showing a woodpanel on the underside like like in those kids wood puzzles, same goes for other pieces, like the top of the tree and esp the little stone.
I removed all the black and selout from the outlines, there is some black left but not much.
I aa'ed the objects to the background so they would fit in nicely .
Merged two colours into one (body and apples)
Added a new darker colour for the stone which I also used in the tree. Colourcount is still 24.
added some highlights to various things, leaves, treetrunk and so on.
Gave the poor lass a proper mouth and nose and changed the shape of the face a tiny bit.
made the wrist of the supporting hand a bit slimmer
Added some little highlights, waverings on the water (needs more on other objects as well)
Fixed aa on 2 of the reeds and gave one reed a proper shape, reeds are longish and have a bit of the stem at the top most of the time.
Also added some highlight/texture to the bigger reed to give it a feel of fuzzyness.
Pronounced shadows here and there and changed palette a little to unify it a bit more, could be taken further.
Yours -- Mine
I suspect that you always do very clean lineart first and then you add in colour, other than that I can not explain to myself how you end up with this massive amount of Selout. I would suggest to you for your next piece like this not to do any lineart, but instead try to work in shapes.
Block out fields of colour and work from that. In nature there are no outlines and in case you want to do something really cartoony work the outlines into the image instead of breaking them up with selout.
You also seem to only use 1 pixel aa, as in abcd, but it can also be aabbcc or something else.
Antialiasing is always an approximation to fake higher resolution/greater smoothness.
I think if you would take these pointers into account and would perhaps not think so much of "sprites" when you pixel you could advance quite a bit further.
Keep it up
