The Beatles in the 70s, the fab four officially broke up in the late 60s, and on paper around 1976, with no more records until the early 90s, with the hit real love. As we can see the ex Beatles stayed remarkably close, into the 70’s 80’s and beyond. The last photo of all four Beatles together was taken around mid 1969 some time in the late summer around August.
As you can see there are many variations, of the Beatles together during the decade of the 1970s. You can see Paul with John, John with George Ringo with Paul, and so on, but there are no know photographs with all four ex Beatles together. There very well maybe be some unpublished, but non has ever surfaced. That would be cool.
Paul McCartney, Ringo Starr, and George Harrison finished working on The Let it Be the last Beatles album, during the winter of 70, and early spring. There maybe some photos of the session, but I have never seen them, and John Lennon was never present at any of those sessions as far as I know of.