When I was a child, my siblings and I build our own home nature museums using advice from the classic book, How to Make a Home Nature Museum by Vinson Brown, published in 1954. You can buy used copies of this out-of-print book online.
For a more recent take on making a home nature museum, check out Natural History Collector: Hunt, Discover, Learn! by Michael Sanchez, published in 2018. Both new and used copies are available online.
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Here are some web pages with ideas about how to store and display your collections:
The Science Museum Museum has some advice on home nature museums: Make your own museum | Science Museum of Minnesota (smm.org)
Build a Homemade Natural History Museum:
https://childhoodbynature.com/build-a-homemade-natural-history-museum/
Ideas for Displaying Rocks and Fossils:
Here’s a play-based inspiration for parents with young children: https://earlylearningideas.com/geology-lab-dramatic-play
Pinterest always has lots of ideas for adults and older children:
https://www.pinterest.com/beckystone1/rocks/
https://www.pinterest.com/rachelemisiti/fossil-display-ideas/
Ideas for Displaying Shells:
https://www.completely-coastal.com/2013/02/seashell-collection.html
Nature Collector's Garden and Nature's Swap Shop 