How to create an inner frame for the banner?

Hi everyone!
Im looking for help in regards to designing one banner. I would like to create a frame for a banner, not around it, but inside the image, close to the edge and with some elegant corners. Something like a thin white line inside the banner, but with ornamental corners, something beautiful, lotuslike.
Unfortunately I dont have an example to show, but hopefully my idea is more less clear.

Can anyone share their experience, how to create something like that? Or is there some special program or templates to do that? The problem is the corners, to create a simple frame is not a problem.

Thank you.