You can do it with css but remember that it will border the bounding box only - if you have a square or a rectangle it is OK, otherwise not good!
sym.$('yourelementname').css("border", "solid 2px");
An alternate 'hack' using EA UI, aside from Maries sound css routine.
Select the image element and explore/experiment with the Box Shadow properties.
Example below - both Drop and Inset 'faux' border.
- set x, y and Blur to 0 and toy with the Spread integer using a positive value.
- alter color property to your liking. I used black at 100% Alpha.