what is the longest post possible

[Ham Sandwich]

This one is pretty long, but it's certainly possible to do better.

 

[31 Black]

0/10
Not enough Bee Movie script.

 

[We Are The Witches]

The longest post is probably comprised of tall images (not like yours, but far taller) until you max out the 64K character limit. So the only question is how Kiwifarms handles tall images.

 

[Poppavalyim Andropoff]

a photo of my cock