I'm glad you like them!! I can try give you some advice, even though I'm pretty bad at it



shading/colouring is probably one of the most important thing when it comes to making skins



instead of using darker versions of colours, I'd say it would be more pleasing to the eye if you used other colours, like shading orange with red, purple with blue, etc, since shading with dark colours kinda makes it look dull and boring



Although, it doesn't always make it bad to shade with dark colours! All I'm saying is, that throwing in a bit of different colours makes the shading look nicer



I made something that might make what I said make more sense, I don't know if it'll send, but it's worth a go:



I hope this helps!! :)