Images used for sub-categories or articles need to be uploaded by FTP to the default directory you choose. As of now, this is "uploads/mreviews/images/" which is where you should transfer your images.
You may have issues IF you included the path to a category/sub-category image when defining them AND IF you also provided that path in the admin Configure section. I regret any inconvenience this may cause in editing, but now they only require the image name and the system will find them according to that configured path.