Front Row will ONLY look for pictures in your iPhoto library. If your iPhoto library is on a different drive, then it will look there for your photos.
Are your pictures in iPhoto?
The issue is the same with your Music, Front Row will ONLY look for music in your iTunes library. The movies are different. Because there's no one application organizing your movies the same way iPhoto organizes your pictures and iTunes organizes your music, Front Row just looks in the "Movies" folder for files. If it finds an alias/shortcut to another drive, it also looks in there. (Your iTunes videos are also listed in Front Row because it's smart enough to not list them under "Music".)
So, in the simplest terms, yes, Front Row can display pictures that are on a different drive as long as that drive holds your iPhoto library. However, Front Row cannot mix and match pictures located in more than one iPhoto library and/or more than one single location.
-Doug