These shells are mostly from the 50's.  Many of them are hard to find now.  The colored bag is all from that time - about 90% of the mixed beige bag is from then and the individual larger shells are current. 

They are called flower shells because ladies would buy shapes of something like plexi glass and then glue the shells on it to make flowers and leaves.  They would then glue a pin back to it or earring backs, etc. I made a primitive one just to give you idea.  Searching the web I found many people are now making pictures - really beautiful.  

They also made dolls.  They would paint a larger shell (unfortunately I only had 4 of these left so i can't guarantee you will get a face, but you can easily paint something similar)  They would have pipe cleaner arms and legs many times - but also some more substantial bodies.  They were then dressed in all kinds of shells!