Hi Carl,
I have one or two ideas that may help you, involving floating text or a small second image. It's late here in the UK now but I will give a full answer tomorrow.
Here's what you can do and I made some screen shots, see below.
The first two shots show both floating text and a "logo" image placed in the outer border. The latter requires the page to be set to freehand mode before dragging the logo image to the preview; the page editor was then used to position it accurately and make sure it was "in front" of main image.
If you are making sets of canvas wrap prints of identical sizes then it will pay to make a template for each size with the logo text and or image in position. Once done, all you will need to do is drag the main image to the preview.
See second pair of screen shots.
If you are not sure about how to do any any of this, especially templates, please come back and ask.
Terry