There have always been more mysteries around than decades available.
This Orthodox Rosary includes three mysteries not in the traditional Rosary of Dominican Alan de Rupe or the five Luminous Mysteries of John Paul II:
1) The Birth of Mary
2) The Presentation of Mary in the Temple
3) The Flight into Egypt
The Franciscan Rosary from the 15th Century includes the mystery of:
1) The Visit of the Magi
It totals 7 decades of 10 Aves, plus two extra at the end are to symbolize the 72 years of Our Lady's life on earth.
Then there is the mystery of the Circumcision from the Chaplet of the Precious Blood.
Gathering all that up together, it wouldn't be hard to add yet another five mysteries to the Rosary, over and above the five Luminous Mysteries. To whit, the Joyful Mysteries could be increased to two sets of 5:
1) The Birth of Mary
2) The Presentation of Mary in the Temple
3) Annunciation
4) Visitation
5) Nativity
1) Circumcision
2) The Visit of the Magi
3) Presentation of Jesus in the Temple
4) The Flight into Egypt
5) Finding of Jesus in the Temple
I wonder how many other mysteries can be found on various Rosaries? The Precious Blood Chaplet also has the Piercing of Christ's side as the last Mystery. I suppose you could include the Assumption of St. Joseph and the Espousal of Blessed Mary. There must be others.