To discreetly personalize a work, add your initials and the year. Use a backstitch at the edge of the design with a floss color that is readable, but blends in with the design. Do not mat over it, but instead allow it to be seen! It's always fun to look at your finished pieces and know when it was completed.
More detailed information could be added to the edge of the fabric where it will be hidden after framing. This information may be found years and years in the future and could be helpful in identifying when and who did the needlework.