Nicholson was born in Scotland, and studied at Duncan of Jordanstone College of Art and Design (which later became part of Dundee University).

Following graduation, Nicholson became a freelance illustrator, but found "the work was meagre, so I had to find a weekly paying job, this came in the form of an advertising sweatshop (so to speak) in London, with very little money.

He also illustrated many creatures in the Fiend Folio, the original UK contribution to the first edition of Advanced Dungeons and Dragons,[2] including the cover art.

[4] For over forty years Nicholson produced work for a wide range of companies and publishers, including Puffin, Pan, Collins, Hodder and Stoughton, TSR,[5] Games Workshop, Hoggshead Publishing, DC Thomson, Le Grimoire and Scriptarium [fr].

In addition, he drew the album cover (False Weavers) for Santa Cruz anarcho-folk punk band, Blackbird Raum.