theme_imagecache_formatter not a registered theme function

I'm trying to override this "theme" function and I can't because it's not being registered in hook_theme(). I noticed that sub theme functions of this are created (and registered) that just then call theme_imagecache_formatter() as the function call. Can we instead call theme() with 'imagecahce_formatter' as an arg or something?

I need this so I can add the flag link in the image output from filefileld. It doesn't look like there is an overarching theme function for imagefield output. If anyone has another suggestion, I'm all ears.

Once I'm done with the module, we can use flag module for filefield images :)