For those interested, I think I found a workaround solution to my problem.
Another poster was correct that lowering the resolution of the photos would keep them from blacking out. Only problem is that I need that resolution because I’m panning and zooming in on them.
Now since my video footage has never blacked out on me like the photos were doing, I thought what if embed my photos into a video (a few frames each) and then just stretch out the time as needed per photo? So in order not to lose any resolution, I created a new after effects project with a video window of 2400×2400 – which is more than enough to contain any still I have. I then dumped in my still photos and gave them about 5 frames each. Exported that as an uncompressed avi video file, imported that into Premiere, and cut the video up into individual photos. Now that the photos are really video, I get no more blacking – but I still get to work with high rez photos. It’s definitely a workaround, but it seems to work…