The nice thing about todays design style is that, anything goes. Out the door are the typical suggestions and ideas about how to decorate, including size rug to use, what room has to serve as what room, etc.
My son and I spend a lot of time doing different types of exploring things. We go to the beach, the backyard, the park, the flea market, and pretty much anywhere to find various treasures. So the question always becomes what do you do with them? You don't want to clutter up everything right?
Well in come a few ways to de-clutter and still hold onto those items. Get some different size glass jars, lids/no lids, and fill them up with the shells, feathers, rocks, beads, etc. These small items are fun to keep within reason, and fun to reflect on but in a nice pretty jar. Please the jar on the mantel, the bookshelf or in your child's room where they can see it to bring back those memories.
Frames are also a good way to display different artwork that has been created at the various fairs, or during family outings. A hallway full of shadow boxes and framed (without glass) art work is fun and interchangeable.
Depending on the items we have collected sometimes my son uses shoe boxes to store those items, you can decorate the outside of them, label them and then store them in your child's room where they can look into them when they choose.
There are lots of creative ways to keep up with your treasures, be creative, find something that works for your family. That in and of itself can be a treasure hunt.