One of the stamps featured an engraved version of a picture of ABBA, taken by Anders Hanser.
This is what the Swedish Post Office said about ABBA:
Whether Sweden's most successful music machine, ABBA, can also be regarded as genuinely Swedish, is perhaps a question asked too soon, but that it has a very special profile in the enormous world of pop music, no one can deny. A certain cool, Nordic tone is one of the finest of the distinguishing marks of those four people, together with their devastating professionalism. Even if the quartet is disbanded and the ABBAs go their several ways, they have made a permanent place for themselves in Swedish musical history.
I have three pictures on these pages: a picture of the first day cover, a picture of the stamp itself and a picture of the complete set of five stamps.
Hover over the thumbnail pictures if you want to see the normal-sized pictures.