Or, you could find textures the thousands of resource packs that are 16x, fantasy/rustic, and combine aspects simply by dragging the textures around. Just an idea.
Unless they were playing on an older version of Minecraft before 1.5-1.6 then that sort of chunk generation is not a "bug" or a "glitch," it would be due to the fact that every version, the way a world generates changes which means it could cause chunk errors like this, however, the only real way to fix this would be to never update your world.
This can't be due to a "memory leak" because Minecraft world generation uses seeds which means two seeds will have the same world generation, even with plugins.
