I have two variants of this. The 'things from nature' basket which just has shells, wood, stones, feathers etc and 'natural objects' basket including many items from here. This was an easy place to start.
Smell bags for baby Treasure Basket. Contents: green one contains mint tea bags, purple - lavender, brown - clove, rose - rose petal. To keep the smell - store them in zip-lock bags, only take out when using the treasure basket.