Thanks ! The "easy" part is that the sprites are really small, so they tend to be a bit abstract and naming them is the best way to see something in them - as you said, moving a pixel can make a huge difference but putting a different name on the sprite can also make that difference, so it wasn't that difficult to find something interesting each time. I mostly drew random shapes and then thought about what these shapes might be, and how they could relate to the story (and sometimes I eventually tweaked the shapes so they could be more expressive).
I'm sorry my answer is so late, I just never saw your comment until now... But thank you for your comment and I'm happy you liked the game :)