Rule 34 - to anyone not familiar with le 4chan maymays - is a phrase used to refer to the rule of the Internet that, if it exists, there is porn of it. The concept is widely used by many to engage in their weird and twisted desires to see freaky porn, but the establishment of a site for this very purpose can help those that are interested in futanari get their goods with minimal effort. Note that while in other porn communities you might be an outcast, here at Rule34.xxx - futanari is about as vanilla as it gets!
The site does have a few weird scenes clipped in this genre, and the low-effort quality of the images is likely a result of the fact that you can upload your own content. I've linked to a search for 'gay' and while you might think this would have a lot of guy on guy action, most of it is actually of the futanari persuasion. Anyway, I'll stop talking and let you visit this bizarre collection of porn images.