A pastiche is a story written in the style of another author, using his themes and characters. Any Conan story not written by Robert E. Howard is a pastiche.
Likewise, stories about Sherlock Holmes that were not written by Sir Arthur Conan Doyle are pastiches. Thre are Tarzan pastiches, Perry Mason pastiches, Elric pastiches, V.C. Andrews pastiches and many others. If a character is famous and liscensed, then it probably has been pastiched.