Is it possible to link directly to the File Manager from the admin interface, so clients can upload images without editing a page?
One trick I've used is to create a non-executable template - upload-image.php - dedicated just to uploading images. It has a single image editable that is used solely to gain access to the uploader.
If you were more adventurous, you could poke around in the code to figure out how the uploader is being triggered, then add an "upload" button to the admin panel with a custom theme.
And of course, you can always get to the file manager through any image editable. You don't have to edit the page.