I would've never thought to use river rock at the base of potted plants/at the edges of the patio, but maybe that could work. A larger, flat top rock could even act as a riser for a led candle lantern, etc.
23 Amazing Decorating Ideas for Small Balcony I like the wall and tall tree. Maybe cover one wall with the brown burlap or flowery white fabric? Use a fake tree? Can I put fake branches between benches in corner? - Decor It Darling