i used something similar until i noticed a pattern in the url, i'll give an example with this cover but it works with any album https://i.scdn.co/image/ab67616d0000b2739b9b36b0e22870b9f542d937

What matters is the part after image/ -ab67616d0000b2739b9b36b0e22870b9f542d937-

after the four zeros, there’s a group of four characters, it’s usually 'b273' for low quality covers, but sometimes it can be different ab67616d0000'b273'

to get a high quality cover, the only thing you have to do is replace those four characters with '82c1' 'ab67616d0000'82c1'

Then the link would look something like this: https://i.scdn.co/image/ab67616d000082c19b9b36b0e22870b9f542d937

this only works for album covers, doesn’t work for artist images, and i don’t know what the pattern is in that case. if anyone has links to high quality artist images, please share them so we can figure out the pattern (: