Would you like to have more skulls, but don't want to spend more money?
Making a copy of a skull is very easy and cheap to make using papier mache!
I used one of my 10" foam skulls to start out with.

First, apply aluminum foil to the skull to keep the
papier mache from sticking to the original skull.
(it doesn't have to be perfect, but make
sure you detail the eyes, nose, and teeth).

Next, apply a couple of layers of papier mache.
Let it dry for about 36 hours.

Once it's completely dry, take a very sharp knife
and carefully cut down the center of the skull (pic 4) and gently
pry apart the papier mache.
Tape the halves back together and apply an extra layer of
papier mache to hide the cut mark.
Once it's dry, it's ready to be painted! I used some leftover stone paint.

*If you are planning to use it outside, I would suggest
that you give it a few coats of water resistant polyurethane.