It is VERY hansome! The fabric from 20 years ago is just fine to use with today's fabric. If someone told you not to mix fabrics from different times, it means from a hundred years ago or so.........!
Fabrics are just used to date a quilt if you didn't put a dated label on the back, not to determine the value of the quilt. If someone was trying to 'date' your quilt, they would say....the fabrics in the middle are from........ and she finished it 20 years later with this border. It would NOT take away from the value. Make a label with all this info, and sew it on the back.
A woman from the Smithsonian visited our quilt guild and she lamented the fact that people don't put enough info on the label.
It should include your name, was it made for someone, and the event, the date started and finished. AND....WHERE the quilt was made: town, state, anything that can really ID it later.
Yours is beautiful, and you did a great job!