I think you are confusing the activity of core graphic design, with that of the graphic designer and art director. When the designer of a record sleeve places any material on a sleeve, he does so because in his opinion the material is the visual realisation of a message that 'positions' the band. The message can position the band in many ways, which when combined with how they look themselves (or don’t look in the case of Joy Division as they never appeared on their sleeves), how they sound and together with the chosen title of the record, creates an infinite number of possible outcomes. Whether the designer chooses to use a photograph, illustration or element of graphic design by himself or others is irrelevant in terms of intellectual originality.
When, in 1979, Peter positioned a small obscure diagram of pulsar waves received from space (incidentally provided by the band) in a square of black void, juxtaposed against a mysterious title set in unusually small plain type on the reverse, it both reflected and created an unfathomable image of a band and a music that still lasts to this day.
The enigmatic quality of Unknown Pleasures' design has rarely been equalled, and created a wave of copycat designs throughout the 1980s. It would be fair to acknowledge that many of these designers used original graphic material created by themselves, not “borrowed” from a book or painting, however the intellectual originality was totally lacking.
Whilst this type of design activity falls into the remit of many graphic designers, it is more of a creative direction role which involves the nuances of ideas and messages sent out through visual material to create or alter the perception of a particular product or service in the mind of the recipient. This is distinctly different from the ‘craft’ of graphic design, which could be considered to be a number of different abilities involving the production of words and images with one’s own hand.