Thanks a lot for all the help. Before I changed the images' width property, I tried doing it with scale. Problem is, it looks like the orientation gets all messed up, don't know why.
Following your advice, I did a codepen copy of the website (minus the images) for you to see. Notice the (horribly) colored images on the right of the screen when you scroll.
Regarding ScrollMagic, thanks for showing me that it is possible to do it with GSAP natively! I'll definitely take a look into it.
Thanks once again for the help.