That would require a customization and not a simple one, but yes it is possible. Defintely not with a plugin, because none would know where to find the pictures in GD tables.
You have 1st to remove the action that adds the GD slider:
remove_action( 'geodir_details_main_content','geodir_action_details_slider',30);
Than copy the geodir_action_details_slider function that you can find on line 969 of geodirectory_template_actions.php file.
Paste it in your active theme functions.php, rename it to something like my_geodir_action_details_slider (very important) and edit as you wish.
Once done with your custom function, add the action back with your new function name:
add_action('geodir_details_main_content', 'my_geodir_action_details_slider', 10, 1);
That would be it.
Thanks