Thank you so much, eishiya! I just finished the next rendition so I didn't have time to apply your advice for skin tone, but I'm hoping I fixed the pillow-shading a little bit. Your advice is greatly appreciated - I'll be using it! :)

The "preview" text in your preview image is not pixel art (NPA), which is probably why this piece is still on the queue.

They look a bit pillow-shaded, and the contrast on them is poor, the light shadow colour is barely noticeable at 1x, and on the lighter ones, it's barely noticeable even at 3x.

Re: inclusivity, it looks like you're aiming for a specific ethnic group with each base, which I don't think is the best idea. Your bases all have the same facial features and eye colour, so you can't convey any sort of variety of features, you can only use colour. That is something you can use to your advantage! It means you can stop thinking in terms of ethnicity and just think about the whole gamut of human skin colour. The same colour can work for many ethnicities because the features are where the differences lie. So, what I would recommend is to have two "gradients" from light to dark, one with a warm undertone, another with a warm undertone. That will make each base more versatile, as well as cover the human gradient more evenly than you currently do. For an even smoother gradient, you could make the cooler versions have a slightly different value (darkness/lightness) from their warmer counterparts, since with just 8 skins, people would expect to compromise a bit anyway.

If you don't know what I mean by undertone: even within a single family of people with similar skin tones, some people have skin that feels relatively cooler in colour than others. This is true for all skin types, although if you look it up online you'll mostly find photos of light-skinned models. Undertones are usually used in the contetx of make-up, but they're very useful for art and customization in games as well. The lack of undertone variation is what makes even highly-customizable games look a bit bland, everybody just looks like they're from the same gradient, which isn't what real skin is like. Here's an image from a make-up tutorial that shows a range of skin colours with different undertones. Of course, if you use these, keep in mind that for a game with small sprites, you'll want a bit more contrast (including warm/cool contrast) than in reality, and that different skin tones call for different levels of contrast.