Where are the images being uploaded to? Have you checked your asset folder under the "Files" menu item on the left hand side?
It could be that Silverstripe sees that directory and you can control that directory from the File manager and you can delete, change, and add more files in/from there?
If that doesn't work then you may have to code those features into this custom page?
I'm still learning quite a lot, but what I've said above is just an idea to check out.
It just clicked to me that the file manager would only pick it up if your images folder you created to keep those images, might only show up if they are inside the assets folder? If not then you definitely might have to code those features in (delete, edit etc), something I'd be interested in in the future as well.