I was pretty sure this was a render issue, but how would we render the video. I also suspected that the problem was from using different sizes of media in the timeline. For example, the opening video clip, created in Keynote and rendered out as a 5 second (or so) Quicktime Movie was at 1024 X 768. The majority of the photos were smaller than that. I suspect that the project took it's "dimensions" from that initial video clip and the smaller photos then "slid" off the larger screen.
Anyhow, the solution is one of two things.
I was able to successfully render the movie at 640 X 480 - typical 4:3 - TV resolution. In effect, I'm rending it out in a format that meets the requirements of the smallest media used. Actually, I could probably have rendered it out somewhat larger, but 720 X 480 still cut off the images so fiddling around between 640 and 720 just isn't worth it.
I think a better solution is to work in the correct resolution from the beginning. I'm beginning to be a big fan of using Keynote to create the basic slides, exporting the slides as jpgs or pngs and then importing them into the video timeline. This way you know everything is consistent. In the case where, for example, you set your frame size in Keynote at 1280 X 720 (HD - 720p video) and the photo is smaller, you can "mount" the photo on a nice background and render out a composite image that will work perfectly in the Premiere timeline.
So...I learned something new today and am passing that knowledge on to you.