A limner is an illuminator of manuscripts, or more generally, a painter of ornamental decoration.
From the en.wikipedia.org
Dame Elizabeth, the Queen's painter and limner in Scotland, turns 80 this year and the show spans six decades of her career.
From the guardian.co.uk
Limner is also the term used to describe unattributed portraits commissioned by colonial America's rising mercantile class as status symbols.
From the en.wikipedia.org
More examples
Portraitist: a painter or drawer of portraits
Limner is a term applied to the art of untrained and unnamed painters of the American Colonies, or to the artists themselves. Typically the art is ornamental decoration for signs, clock faces, fire buckets, fire screens, etc. The term is derived from illuminator.
A name for an artist from the root word illuminate, used in Britain and in eighteenth-century America. Colonial artists or limners, often working in a naive style, produced the first American portraits, still lifes, and landscapes.
Specifically a portrait painter or a book illustrator.