The way powercms is designed is to store the images in the cms folders. You can change the path where it looks at the root of your site by going to admin/common and open the listfolder.php file and change this line of code:
if(file_exists($parent) && strpos($parent, $root_folder) !== false) {
to
if(file_exists($parent)) {
this will let you browse outside your cms files.