These oceanic-even-when-they’re-not Wall Tiles might be the answer. Organic, serene and edgy at the same time, they don't even sit on a mantle.
Sculptor Heather Knight and her Element Clay Studio have been seen on AT before with nature-inspired bowls. Like them, the Wall Tiles are made completely by hand out of porcelain clay. They feature a keyhole for hanging.
Tiles are available in two sizes, but there's also work aplenty (bowls included) at her Etsy shop. And if geographical appropriateness matters to you, fungi and turf are pretty universal.