You can buy black marbled contact paper at Wal-Mart. It has the veins like marble but it might work.
I've never seen black, but I have colored white with a permament marker and
cut it out. Make sure to put somekind of sealentor the paper can peel off
with time. Make sure if you use a permament marker, the sealant does not make
the ink smear. You could also use paint to create the dots.