It gladdens my heart to see anyone worldbuilding around BLUEHOLME™, and some "fan efforts" are what can only be described as stunning. Take Edward Kann's Warholds of the Northmen, for example, in a corner of his game world where he plays with BLUEHOLME™. He previously detailed his Kingdoms of Daria and Kyrene using the Swords and Wizardry White Box rules by Matt Finch.
Many years earlier, Adam Muszkiewicz's posts about the Implied Setting of BLUEHOLME™ on his Kickassistan blog caught my eye. It's actually quite different from my own Known World setting, but it's interesting to see how others see the rules come to life in their game world. This is one of the reasons I didn't want to tie my own setting into the core rules, I want referees to remain unfettered in their sandbox.