I would do it by having a slideshow table:
slideshow_id int unsigned not null auto_increment, slideshow_title varchar(128)
then a table called slides: slide_id int (etc), slide_title, slide_path
(slide_path is the path to the image file)
and then have a join table which just contains slide_id and slideshow_id (call it slides_to_slideshows)
then if there is an entry in that table like 1,12 it means that slide 1 belongs to slideshow 12. This way, you can also have 1, 2 (slide 1 belongs to slideshow 2), and 3, 12 (slide 3 belongs to slideshow 12) so any slide can belong to any slideshow and vice versa.
then your sql will be something like:
SELECT slide_id, slide_title, slide_path FROM slides AS s, slides_to_slideshows AS ss, slideshows as ssh WHERE s.slide_id = ss.slide_id AND ss.slideshow_id = ssh.slideshow_id AND ssh.slideshow_id = '". $_GET['id'] ."'";
This might seem complicated, but it is worth doing it properly.