Here is a cool feature that can be looked at in different ways.
When you upload photos, on the upload screen you can select to add a black or a white border to all the photos you select in the upload form. Simple enough.
If you have photos already uploaded and you wish to add a border to them, click on the "Show/Hide photo Detail Editor" underneath of the photo. That will expand the editing options.
There you will see these clickable options
Click on the border of your choice. If you change your mind, just click on the link that says "Click to remove border".
Important note. If you click to remove border on a photo with no border, it will shave x number of pixels from your image.
Remember, once the page reloads, you have to refresh the page to see the image.