How to use a collection of small sea shells?

You can decorate with them:

https://www.bhg.com/decorating/seasonal/summer/seashell-style/

https://www.pinterest.com/pin/98657048061291132/

https://www.completely-coastal.com/2013/02/seashell-collection.html

Or crafts:

https://www.marthastewart.com/275561/shell-crafts

http://www.bystephanielynn.com/2011/07/60-different-shell-crafts-for-your-collected-beach-treasures-saturday-inspiration-ideas.html

My master bath has a seashell theme. Love seashells! 🐚

Glue them on a picture frame and put a picture of you at the beach in it.

Get a string of outdoor lights and glue the shells on them, looks amazing

Pour them in a vase, shadow box, get a glass lamp base and use them to fill the base (just run electrical up the center).

Dig into Pinterest and look up shells. Just don't get lost in there for weeks at a time! LOL You will find more ideas than you know what to do with, and when your pieces are done, you can put them up and others can see your work and be inspired!

Glue to a frame of a photo of your family at the seashore, put in vase with colored sand and faux succulents, any rocks if you collected any too, glue to top of small wooden boxes and give to grand kids or nieces as jewelry box or trinket box of holidays, put in large clear vase lamp for decor in den or front room, glue to bobby pins for hair decor for young girls, make a table center piece with them for family meals or self serve banquet type meals with family, bathroom decor

What we do is use them on potted plants, face down, they keep the plants moist and prevent evaporation of water. As a plus, they deter squirrels from digging in them.

Have seen some talented people make slices of them and display them as a flower in a complementary frame and background.

You might make mosaic cement stepping stones, frame a mirror or picture frame, or use as a vase or bowl filler.