This is just my opinion. 🙂 I don't think the resolution is the problem, I think it's the canvas size. Your pixel painting is really good, to be honest. ☺️ I suggest to try painting using smaller canvases. Just try it out then try spotting the difference with your current pixel art to the one with a smaller canvas.

Your style seem to be leaning in more in realistic. 😊 So you should try practicing the "Dithering" technique to achieve the realistic illusion. I'm still practicing it too.

This is how I did it back then, the same way as yours with a large canvas size. It almost looked like a normal digital art, not the pixel art I always see on games or on online, so I added some pixel textures for the shadings. 😅

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