Let\'s say we have a slideshow of pictures. the thumbnails of those pictures are showed in div wrapper with a slider (that I created with Jquery) and each image is included
well, i think that maybe you are making things too complicated. I'm not really sure why you're using css background when the images could be inside a tag. You say the reason is because your images are dynamically created... and i dont understand that.
What you could do is create a page that returns the images, maybe you could use some parameter... something like the image size:
http://www.mysite.com/create_image.php?size=200x100&id=img1
then all you need to do is put this url inside the SRC of the img tag... If you want to, you could pre-load the image when the page is loaded..or when your slider is moving
Or maybe i didn't understood your problem =D