Some ideas include:
-Small stones or pebbles
-Small antique door knobs
Just clean the top of thumbtack with alcohol and do the same to the part of the item to be glued to the thumbtack to ensure a clean gluing. Use of epoxy is suggested, however, goop or super glue can be used for some items.
Enjoy your new addition to your bulletin board…. it will show your personality and uniqueness by adding charm or flare to an area of your home that is surely busy. I hope this brings a smile to your face every time you see your little creations.