The University of Vienna has put up an online Datenbank literarischer Bildzitate, a database of some 1,500 references to works of art in modern German literature, searchable by author, artwork, artist, and text.
(See the search page, which makes it reasonably obvious what's on offer.)
I'm not sure how comprehensive this is (yet) -- Bernhard referenced specific works of art in only one of his novels ? -- but it's still fairly interesting and even somewhat useful.
I'm not sure how comprehensive this is (yet) -- Bernhard referenced specific works of art in only one of his novels ? -- but it's still fairly interesting and even somewhat useful.