To get category images to display found I had to modify the following lines of code:
File: listing.php line 36
from: if(JFile::exists($this->image->getPath($this->element->file_path),false)){
to: if(JFile::exists($this->image->getPath($this->element->file_path,false))){
File: image.php line 38
from: return $this->uploadFolder.$path;
to: return $this->uploadFolder.$file_path;