River rocks are beautifully smooth and are great natural decorating materials.
There are many beautiful ways to decorate with pebbles.
Similarly to the pebble placemat idea you could make trivets and coasters as well.

The DIY pebble trivet requires only some pebbles and a couple other household items.
It will be the cutest thing in your kitchen when you obtain it.
Plus, the coasters wont stick to your glass when you pick it up!
Another popular item people are making with pebbles/river rocks are bathmats and they are simply stunning in a bathroom.