aww,this is lovely!the proportions and face expressions are really well done and you have a lot of talent.However i suggest you use a fineliner (or a black pen) to outline the edges,they seem a bit blurred and a lineart will make it even cooler!I hope this helps you improve :D

looks really good!i love that u made effort into getting the poses right.u still need to practise a bit and if u do,im sure u´ll eventually have more skills ^^

looks cute! Although you look like u have problems w/ anatomy,i suggest u try to learn and understand how bodies work and then u would create a drawing with an actual body.Understand me,a single head doesnt give an actual representation of the character (as a body pose would do)
i hope you keep learning and become an amazing artist!^^