i've seen these bib style necklaces in stores like f21 and charlotte and tried them out for myself. this is one of those mindless DIYs that you can do while watching a movie (<3 that!)
what you will need:
a black sheet of felt [which can make 2-4 necklaces]
black satin ribbon
a package of mini plastic jewels [from any crafting store]
place the jewels on the felt creating a pattern of your choice [the different patterns within the package you get will help to define shapes]
after you have a design you like, glue the jewels down.
finally cut around the jewel pattern you've created
cut 2 pieces of ribbon to the desired length and glue to the back of the felt pattern.
these necklaces 'jazz up' plain black or white shirts [colors that i'm attracted to mostly due to genetics-my mom loves black and white because it 'goes with anything!']