well, not sure if this gonna work, but it worth to try.
open includes/constants.php file.
Find:define('MEDIA_DIR', 'data/media');
define('THUMB_DIR', 'data/thumbnails');
define('MEDIA_TEMP_DIR', 'data/tmp_media');
define('THUMB_TEMP_DIR', 'data/tmp_thumbnails');
define('DATABASE_DIR', 'data/database');
define('TEMPLATE_DIR', 'templates');
Replace with:define('MEDIA_DIR', 'gallery/data/media');
define('THUMB_DIR', 'gallery/data/thumbnails');
define('MEDIA_TEMP_DIR', 'gallery/data/tmp_media');
define('THUMB_TEMP_DIR', 'gallery/data/tmp_thumbnails');
define('DATABASE_DIR', 'gallery/data/database');
define('TEMPLATE_DIR', 'gallery/templates');
P.S. I'd like to know how did u the trick with include...if u changed some include in the 4images code, u'll probably will need turn it back with changes above...