Thank you Kolja for your honest opinion and criticism. You are absolutely right. However, there are two things that most of the time keep me from doing more details, highlighting, layers etc.:
1. The size of the miniatures like this one is 38mm, which is quite small in my opinion. More detail is mostly visible only under a magnifying lense (at least for my eyes) with which I am already working for this size of miniatures. BTW, the bigger the miniature, the better are my voting results (the best is biggest in size)
2. The "cost-benefit ratio" if this makes sense in the given context. I rather stop when the result is OK/good in my opinion so that I can continue with the next miniatures in order to finalize the given set (which is always from a certain board game). I started painting end of last year only to enhance the gaming experience for me and my friends. So I am showing here what I did because posting my results kind of keep me going even if they are mediocre ;)
Your minis are all cleanly painted, but to be honest they look a bit like works in progress that are waiting for more layers of highlighting and shading. You started to apply some highlights and shades, but I would encourage you to go further with that: more highlights, more shades, and much stronger variation between the base colors, the highlighted and the shaded areas, so the mini starts to look more three-dimensional and more "3D". On the other hand (maybe a matter of personal taste, sorry), the attempt to show eyes with white eye balls and dark pupils, and the mouth with very dark red lips, looks very loud compared to the rather "flat" skin.
I hope you can read this as an attempt at constructive criticism encouraging you to aim higher, not as a way to discourage you - it's clear that you have quiet hands and an eye for detail so I'm sure you can improve very much very quickly.