the hands are too short , the shoulders are too narrow (?)
oh and the nose should be near the eyes , not on the cheek. the eyes are way too big , make em' a little bit smaller.
also you should work on the hands anatomy , i think you should look on google at skeleton hands , also sans' chest should be wider .
as for the coloring the background pops out , and you should do some shading with dark blue , not grey , but i believe you can do better. i hope this helps
i can see some effort has been put in this piece , so keep trying , i am sure you'll get better , i hope this helps