Alright, I found a solution, altho I'm still unsure of something, I understood at least that we can just wait and refetch a message to get any image URL from the embed's image. I just didn't fully understood they were actual embeds.
What I just don't know is how to see the distinction between an URL that creates an embed for say, a website vs an URL that gets replaced with an image embed :shrug: weird. I guess one could check if the embed has a title or other stuff like that to know if it's only an image '^^