Your current slideshow is really just an animated gif. You should be able to find a graphics program that will let you edit such gif files on a frame-by-frame basis so you don't have to always "start from scratch" and do just fine. The alternative would be to find a JavaScript slideshow. Such scripts generally include a list of individual images to be displayed, and some have the capability of displaying all of the images residing in a specified directory on your site. The web is full of them. Just try searching on "Javascript slideshow".