By the looks you do have a large collection of duplicate images, from what I can tell there appears to be for instance 23 versions of sydney_logo.png in uploads for 2019, same goes for testimonial_author.png in the same folder.
Before going ahead with adding space you would need to clean up a bit, especially since these also appears to not be used on the site.
Yes the files are small, but you have over 2 500 images in that folder and there's that many duplicates it will add up quickly.