2011 Update: this post is so old that most themes now have Post Icons built in. Tiffany (below) no longer uses the Post Icons, but I’ll leave the link to the video tutorial below just in case you were dying to see it. ;-)
Another fantastic plugin from Didzis, this one called My Post Icons. This plugin allows you to assign a certain image to a post (much category icons does) and let’s you resize it, give it some CSS formatting, etc. Perfect for Tiffany Hawk who uses it for an image of her magazine covers or photos of her profile/interview subjects. Here’s a help video to walk you through how to use it and a bit of behind the scenes to see how it can work for you if you’re a designer.