Contrary to popular opinion, simply putting a whole load of (e.g.) digital camera images and running them through Nero or whatever, can produce either quite respectable results - or simply awful - or anywhere in between. You seem to have fallen into the 'awful' category. :-(
The potential reasons are various and involve the image(s) size, their aspect ratio, the CD/DVD player, the medium (CD or DVD), the software used, etc.
However, the good news is that, by 'pre-processing' the images before committing them to a CD/DVD, it is /always/ possible to produce excellent results. Magazine articles have been written on this topic but, unfortunately, are not on the web.
We'll be glad to assist but, to help us to help you, please could you fill in the following details:
a) What typical size are the images (in XxY pixels).
b) For avoidance of confusion, have you actually burnt a 'video-slideshow' onto VCD, or have you copied the images onto a CD (as datafiles), to run as a slideshow on a CD or DVD player?
c) Are you trying to display them on a 'domestic' DVD player? (If so, what make and model please?)
d) Have you 'pre-processed' the images, i.e. first scaled them down to PAL size and aspect ratio? (From you reported symptoms, I guess not).