New Zealand is attempting to cash in on the release of Peter Jackson’s The Hobbit films with a set of special-issue coins featuring Gandalf, Bilbo Baggins and other characters from J.R.R. Tolkien's fantasy classic.

The Hobbit coins, including a gold set featuring Bilbo Baggins, Galdalf and Thorin Oakenshield, will be available Nov. 1. (New Zealand Post)
New Zealand Post, which is issuing the coins, is aiming for the collector market with the most expensive of the coins: made from one troy ounce (31.1 grams) of pure gold and selling for $3,695 NZ ($2,957 Cdn).

A set of three gold coins — depicting Gandalf, Bilbo and Thorin Oakenshield — sells for $10,995 NZ ($8,798 Cdn), but each coin will bear a face value of just $10. The rim of each coin is inscribed in both English and Dwarvish with the words "Middle-earth — New Zealand."

You'd never get that over here, but there's no reason why we couldn't have JRR Tolkien on a future bank note.
As I understand it they have to be :
A) Dead
B) A contributor in a major way to society.
Writing the most popular fiction book of the 20th century satisfies the second criteria for me.