This is awarded upon completing the seven ‘Body Art’ Side Quests issued by Francesca in Beverly Hills. Each quest will require a certain zombie part (or two).

For the first quest you'll need to deposit 10 chunks of infected flesh, 5 oversized arm bones from Crushers in the second, 5 chthonic ichors from Slobbers in the third, 5 infected spines from Screamers in the fourth, 3 blade arms from Butchers in the fifth, and 3 mutated hearts from Mutators in Francesca’s bucket in her garage for the sixth and final fetch quest.

Finally, after a little time has passed, Francesca will then reveal her horrible art piece and this will unlock. Not only that, but you'll earn another one of Dead Island 2's Legendary weapons.