One of the surest tests [of a poet’s superiority or inferiority] is the way in which a poet borrows. Immature poets imitate; mature poets steal; bad poets deface what they take, and good poets make it into something better, or at least something different. The good poet welds his theft into a whole of feeling which is unique, utterly different than that from which it is torn; the bad poet throws it into something which has no cohesion. A good poet will usually borrow from authors remote in time, or alien in language, or diverse in interest.
T. S. Eliot, p. 114 in The Sacred Wood: Essays on Poetry and Criticism, 1920
Likewise, a good illustrator welds the theft into a whole of feeling which is unique, utterly different and sometimes even funnier than that from which it is torn.
2018-02-18, update: 2018-10-06
[left]: Illustration to Lewis Carroll’s The Hunting of the Snark (1876) by Henry Holiday: The Vanishing (detail from lower left side depicting some weeds which seem to have some fun with each other)
[right]: John Martin: The Bard (ca. 1817, detail from lower left side, retinex filtered and vectorized)
In this image one of the elements has been marked (blue frame) which Henry Holiday borrowed from a 17th century painting (by an anonymous artist). This might be a bit different from the borrowing described by T. S. Eliot in 1920. The borrowing ot the pictorial allusion is inconspicuous. It doesn’t enrich Holiday’s illustration. It’s only purpose might be that of a signpost pointing to another work of art.