I find it difficult to decide how to best finish a cross stitch project. For example, I did a cross stitch sampler for my daughter. I could have stretched it and then be put into an 11 x 14-inch frame. I decided instead to take a piece of green material to match the colors of the sampler and sew it to the back. After sewing on the back and turning right side out, I placed a wood dowel at the top to give it a sort of scroll look. Then I finished it off with green ribbon at the top for hanging. This way I saved some money and made a unique gift for my daughter and son-in-law.
With cross stitch on a hard canvas, I have found that no matter how careful you try to be the back always looks a little messy. I would suggest getting some felt in whatever color matches the main color of your piece & hot glue it to the back of your piece. This gives is a finished look especially if it is a hanging piece where the back can be seen.