Alm-Pe said:
Bumping this thread because I'm confused as to how to handle the other link format:

https://66.media.tumblr.com/ac78fe659710db6ea3b92c0ff3837380/a0f8af50b1f001bf-90/s500x750/940984b3753be3a77a86a9125ea02f54b90b1610.png

I've tried messing around with the "s500x750" bit but I just get error messages from doing so.

You shouldn't be taking images directly from the page at all, you should be reblogging and exporting your blog.
Here's the artists whole tumblr blog post exported with raw files: https://puu.sh/E9wCO/6f743f35ed.zip

Looks like the largest available version for some images on Tumblr has increased. Some of them are now available in 2048x3072 pixels.