I'm getting no pictures
Have you tried waiting for several seconds? If your internet is slow and the randomly selected picture is big, it might take a bit of time. Also check if you have network proxy or something similar enabled that might restrict your access to rule34 website content (work proxy?).
If you know how to work with the browser console, you can always open it (F12 - Network tab) and find request to api.rule34 to see if it was successfull or something is blocking it.