He married HRH The late Princess Margaret in 1960 and, after their divorce in 1978, married Lucy Lindsay-Hogg. He and Princess Margaret had two children: David (known by the courtesy title of Viscount Linley), and Sarah. Snowdon was, of course, a very well-known society and royal portrait photographer.
Heraldically, he was assigned a simplified version of his family Coat of Arms as shown above, namely: Sable on a chevron Argent, between in chief two fleurs-de-lys Or, and in base an eagle displayed Or, four pallets Gules. The Shield is encircled by the Riband of the Royal Victorian Order which he was awarded with after successfully organising the Investiture of The Prince of Wales in 1969. His supporters are a griffin and an eagle. His Motto translates from his family's native Welsh as What God wills will be.
During his lifetime his son David was known as Viscount Linley. This is the subsidiary title to the Earldom of Snowdon and it is the custom for the eldest son of a peer to use. Having said that, Lord Linley still ranked as a Gentleman as far as his Coat of Arms was concerned and therefore was not entitled to a Coronet. Linley differenced his Coat of Arms as the eldest son with a Label, his chosen colour being the rather appropriately Welsh green. I have not been able to find a version of his Coat of Arms as Viscount Linley which doesn't, incorrectly, show a Coronet. A courtesy title as the heir to a peer doesn't entitle you to a Coronet and, if he had appeared as a member of the Royal Family in his capacity as Viscount Linley, he would have worn a morning suit, not robes, as he did at the Vigil of the Princes as Her late Majesty Queen Elizabeth The Queen Mother lay in state.
Below is the nearest I can find, but presume this in incorrect as there shouldn't be a Coronet yet, let alone that of a Grandchild of the sovereign through the female line.
We shall see what develops...