Looks good to me. I also like that you showed the animation of the waterfall.

So, with the red elements of the page (like the button), I actually think it might look better if it was the same color as the blue background to the image that talks about Free/Paid versions and what you get. However, if ever in doubt about it… it wouldn’t hurt to get a second opinion, too.

That looks awesome, i might even use that for my games

(Disclaimer: I'm not rich off of the itch marketplace either! I've made a couple hundred dollars, which I think by itch marketplace standards is moderately successful, but it's not paying rent.)

It seems like a pretty cool set! I think in terms of spritework, the only thing that really bothers me is the section of water above the waterfalls. It's unclear to me if you can set it up without having a convenient overhang to hide where those lighter pixels are coming from, and...they don't really feel like a water texture to me. They just feel like random pixels, noise for the sake of having noise, especially the larger rectangular bits close to the edge. I'm not sure they're really necessary at all.

I don't think that's where your problem is, though.

I'm not a game dev, but I think your biggest problem is that it's still just one biome. You can't make a full game with just this--it's a cool aesthetic, but it'll get old fast if it's only the one. Plus there's no monsters and no NPCs as far as I can tell--just Stub and that one rock mimic, and it's not clear to me if the rock mimic has attacks.

So if someone does like your style enough to make a game with it...what then? Since this is your only pack, it's either going to be a really short game without a whole lot of area diversity, or they'll use bits and pieces of it mixed in with bits and pieces of other tilesets, which forces them to find other kinda-compatible tilesets and risk some style clash. (There's times when this can work! It's easiest when you and the other artist are both peeking at the same existing game's notes and your audience is actively looking for that.)

I think the quickest, easiest thing to try is to make a couple alternate palettes that also look good and cave-y, and showcase those in your screenshots instead of keeping the same one throughout. Ultimately I don't think that can really carry a game either, but it'll show people that there's potential to stretch it further at least.

The less easy option is to keep making more stuff.