please read the last 3 posts in this forum thread. I have been trying to get this figured out for days now, but the fellow who designed the theme lives in Bangladesh, so he responds onces a day, and it is not getting resolved.
get you up to date: using css gallery theme. he claims I only need to upload 1 large image. but I uploaded 2, a small and a large to make it work, except for the most recent post which you will see here:
thanks a tone, I've been posting too much about this.