If the images are going to be shown on your own website, it would probably be easier to simply use CSS (especially if your bottom image simply gives a border...). Of course, if you want people to be downloading these files with the frame, that's a different story.
I don't think CI has a built in method in the Image Manipulation class. But, that class is simply abstracts typically-used features from one of the three major PHP image libraries (GD, ImageMagick, and NetPBM). If you know what library you are using (I normally use GD for basic things like this...), then you'll just have to use their proprietary ways of doing this stuff.
You can even make your own library or extend the Image Manipulation class to add your own special features.
Also, there may be ways to do this in Zend (not sure, I'm not going to look it up either). But, there are easy ways to include Zend components into CI if you do find something.
Good luck man!