Start a new image.  Place your photo on the new background.  Go to Layer tab, Layer Style, Stroke.

A screen will open that you can adjust any way you like, any color & size you want, including gradients and patterns.

You can delete the background layer and as long as your photo layer is transparent you should have what you want.

 

“Music is harmony, harmony is perfection, perfection is our dream, and our dream is heaven”
Henri Frederic Amiel