This is a feature request. But it would be huge life saver if hazel to read and write to iptc and exif on image files. You could use the existing exiftools, it makes iptc and exif available in the command line, as a way to implement it with in hazel. (or I think you could but I'm not a superstar developer with the brains to make something as great as hazel.)
If I could apply metadata to my files with haze and use that metadata to sort, it just might literally save my life one day. You might think that statement a bit dramatic. But if I lose some picture files my clients has ties to organized crime, that I was unaware of of-course, you could save my life.
I'm sorry for the far fetched example of what that would mean to me, but it would be seriously great if hazel could do that.