Quoting from [The Jeco]:
Changing the photo in the product will NOT change the sell lead, unless the actual name of the photo is the same, even then it may not update perfectly.I would recommend if you chnage the photo in the product that you also redo your sell leads. (delete the original and do a new one using the new photo)
I would also recommend you chnage the name of the photo so you don't accidently use an old one in a lead.