WOW, file manager looks awesome! It looks a lot easier to navigate huge sites with thousands of files and hundreds of pages like some of my sites have. Very slick and well done! That left admin nav bar is nice too, I'll have to play around more with this.
If I had to give room for improvement it would be nice to see image previews in the file manger so you can see what you are selecting (jpg, gif, png). It wouldn't have to be large, postage stamp size would do the trick. Even if the "icon" view showed actual file thumbs instead of the generic icon image that could work. Not critical, a little thing.