The resolution will not mater,there must only be the photo of the nft. And better to make a physical thing just to keep in wallet near you all time.
if I have understood NFTs then you get a photo then you have to do the real photo uncompressed, which I don’t know what the uncompressed means and why it matters and then you can make from that a collage of those. if that’s the case and you done that then it will be fine by any resolution.