Janson and Gardiner are the tomes of choice for
most Art History 101 classes. However, I agree that
they offer little in the way of biographical info for
the Modern Toss-up. As an art history major, I found
that many tossups in art usually start out with info
that could only be known via the reading of individual
biographies of which there are many for most prominent
artists or from previously having heard a question in the
canon with said anecdotal information. Also, please
note that the naming of paintings is often arbitrary
with names assigned by critics, curators, or
historians after the fact. Since many subjects are popular
throughout the ages, it is often possible to list a bunch of
paintings that could be the names of paintings by anyone.
An example of this phenomenon would be illustrated
if you were to list a number of Bob Dylan songs that
are popularly covered by another group of musicians
in a question asking for the name of the act other
than Dylan. Just my thoughts on the subject of art
toss-ups.