You will need to install a user script manager extension to install this script.
This UserScript is based on an old script called "DailyBooth Original" for the now-defunct DailyBooth; however, all of the code needed to be rewritten to deal with the fact that each Fiverr gig page contains multiple preview images instead of just one, with only a few even being loaded until the navigation feature is used.
Some of the generated image links may point to invalid images, but this is because the manual method of extracting the originals (right-click the little thumbnail, open in a new tab, and change anything like
v2_102 or any other size information to
original) would also return an invalid image; however, this script will not generate an image link if it is not in the smaller-image format mentioned earlier.