Since I mostly edit in Final Cut and am not too too familiar with iMovie, my first thought was to reword all the title screens to my preference, then export the movie into a quicktime (.mov) file [Share -> Export Movie -> HD 720p -> Export]. From there I would open up Final Cut, import that file, drop it into the time line, use the razor blade tool and replace all the placeholder templates with photos. But after messing around some more in iMovie, I found out how to do it without having to do that workaround. In iMovie it's as easy as [File -> Convert to Project]. Viola!
Btw, here's how my project turned out: