With skinning (or art in general) the answer is usually that everything can be improved. Learning different styles etc. can always be beneficial and never stops being something you can improve at (:.

Improvement is not easy to measure and can come in different shapes and sizes. I'll try to just briefly go through a few things.

Shading: your shading currently is very standardized - in the sense that you use the same template shading, no matter what the design is. Generally this is not a good thing - as shading should be used to represent shadows and highlights. To create a texture. Template shading, for the most part does not do that. My tip here is to think, what is the reason you shade (depth? creating interesting variation? design-choices? etc.) and what shading, at its core, actually is.

Colouring: Your colours currently suffer from low contrast issues. This matters because without contrast, or awareness of it, your shading will suffer. This is not to say you can't do well without contrast, but it's an advantage to know when to apply it and when you shouldn't.

I want to bring up another thing: Blending. Many of your skins have palettes that mesh together. This creates a blurry effect, that does not seem to be intended. This is usually not a good thing, as being unable to read your skin, makes the design go to waste.

Another thing you might want to look into is how your palettes value/saturation/hue (or RGB) should change throughout your skin. Sometimes your skins need more hue shifting, sometimes it might be worth it not to hue shift much, if at all. These are all things I'd recommend looking at.

Design: I don't see much problem here, if you want to keep doing teen skins exclusively. Teen skins are great, for the reason, that we can reuse design-assets several times, but get something new from it regardless. That being said, if you want to branch out, definitely give some creative designs a chance. Maybe venture into hat-layers and less human designs sometime, those are always fun c:

Uploading more is the one thing I don't think you need to look at: Upload at your own pace. Rather really well thought-out good skins at a lower rate than many lower-effort skins at a high constant rate.

I feel like you could improve on a bit of everything (like mostly everyone ;'P) but the main odd thing I notice just at a glance is the colours you use. Some of your skins like this skin, have really nice colours, they're similar in a nice way. The fact they're spread around evenly throughout the skin is also quite nice to look at.

But other skins are a different story. This skin looks really off. The colours seem as though they're picked at random. The light green and dark brown seem to be meshing not very nicely. I also notice rather than evenly putting the colours throughout the skin looks very separated, her head being one piece and her body being another. I also notice you use two totally different reds, which is quite odd. Accent colours are very important in my opinion (but some pieces can look good regardless) and I feel as though it might look better with a single accent colour for both and a bit more evenly distributed.

I'm not the best at explaining things but hopefully this helps^^

Maybe try out some skin variants other than teens like animals, mythical creatures, items around your house, or even just characters from cartoons or movies! It can be fun to move out of your comfort zone sometimes and try different things to skin in the long run. Your shading and colors are fine, so I believe you can do it! :D

Maybe you'll like Steampunk style for skins?

Here is a great video about hue shifting for your palettes. https://m.youtube.com/watch?v=RL_5va7jEx8

@ Pastel colored EVERYTHING

Wait you do that already, I think you're doing fine! <3 :D
I do want to agree with Peridot though. Do a little leg stretching with other creatures :D You could do like... pretty pink zombie! Or lavender teddy bear!