[TypeEE]

Find this code in your image_upload_main.php

PHP Code:

         if ($main_smarty->get_template_vars(module_imageupload_filename_field) == "")
        {
                $imageFile = module_imageupload_fullsize_prefix.$storyID.".jpg";
        } else {
                $imageFile = $main_smarty->get_template_vars(module_imageupload_filename_field);
        } 


change it to

PHP Code:

        if ($link->link_field1 == "")
        {
                $imageFile = "MyDefaultImage.jpg";
        } else {
                $imageFile = $link->link_field1;
        } 


You should have MyDefaultImage.jpg in your images directory.