Can I load an image in a character sheet based on a attribute value?

I'm making a custom sheet for a homebrew and I want my sheet to calculate the character's defense based on some other values, then pull an icon for the defense. The file will be like "defense-4.png" if the defense is 4, or "defense-2.png" if it is 2, etc.  Is this something I can do?

I tried something like this with a drop down menu. I couldn't get it to work though. I can guarantee it would require a sheet worker, but beyond that, I'm afraid I'm not much help.

You'd definately need a worker of some sort to update sheet content on a change or trigger. If you're talking about a macro/template output instead of a sheet graphic, that's fairly easy to do.  You just have to make sure you use VERY tiny images and have them hosted somewhere reliable.  (Take a look at Pathfinder Sheet for examples of roll icons)

Assuming you have a finite set of images, you can check out what I did with the Arkham Horror character sheet. On the Arkham Horror sheet, I've got a sheet worker script using a <select> attribute to set a number of other attributes, including a radio button which will show/hide an image. Without a script, you could also have the <select> and the radio buttons use the same name.