In that vein of noteworthy events, I was recently sent some photos from the Franciscan Friars of the Immaculate in Griswold, Connecticut (which friary, readers may recall, switched over to the usus antiquior as their primary liturgical form beginning this past Lent as was reported here in early February) which I think fits the bill.
The photos in question, taken during Holy Week, were, to quote, "the first Solemn Masses ever to be celebrated" at this friary and thus certainly mark an important milestone for that community.
Fr. Santos from Holy Name Church in Providence, Rhode Island and Fr. Murphy from St Anthony of Padua in New Bedford, Mass. assisted in this by lending the friars many of the vestments used for this purpose.