Took the exam 10 months ago so this is a guestimate...
A significant portion (20-40%) had at least some sort of diagram--a chart, a graph, a drawing, a photo, something-- and maybe 10-20% of questions had an actual photo (histo/path/micro/lesion/x-ray/mri/big fat Cushnoid guy)
With the photos, sometimes they weren't necessary for the question; i.e., you could figure out the answer w/o the photo, but the photo gave you the answer if you recognized it. But with the xray/mri type questions, sometimes the question was ridiculously difficult but the image gave it away... I love those.
hope this helps....