Furry stuff, oekaki stuff, and other stuff.
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It's in the control panel under "Enable latest picture log."
You need some simple scripting knowledge to put the information to use, though. The file is just an easy way to bypass having to write your own database query code.
I remember that with 1.5.8 there would be a new file called latest_pic.txt but I have not find that file. Is there anything I have to do for it to show up properly?