Sand the wall you want to decorate with a sanding buffer with an attached medium-grain sanding ring. This make the wall more evenly textured and removes old paint and roughness.
Vacuum the entire wall and floor using a shop vacuum to remove any debris and dust caused by the sanding.
Spread a 3-inch thick layer of medium grout over the entire wall using a trowel. Apply the grout in an even layer.
Press flat river rocks halfway into the grout-covered wall. Select river rocks that are all approximately 2 inches thick. Space each rock 1/2 inch apart. The grout will squeeze out between the rocks.
Scrape the trowel across the river rock-covered wall, which spreads the squeezed out grout over the tops of the rocks to fill in any empty spots.
Wipe off the front of each rock using a washcloth, then allow the river rock wall to air dry for 24 hours.
Paint a layer of clear sealant over the river rock wall using a 3-inch flat paintbrush, then allow the wall to dry for 12 hours.