Few homeowners would want the shapes of fungus, germs or mold to freckle their walls or ceilings. But when Stephen Pallrand, the owner of the architecture, design and construction firm Home Front Build and a dedicated environmentalist, set out to construct his family’s new house in Los Angeles, he chose these intricate motifs.

Printed mycelium, a fungus, trills up hemp drapery; E. coli appears to wriggle across bathroom tiles. At first glance, the kitchen backsplash looks like a graphic, polychromatic holdover from the 1970s. But no, it’s a representation of mold spores.

“There’s a little mischievousness about bringing all these things and making them visible,” said Mr. Pallrand’s wife, Rachel Mayeri, who based the tile designs on electron microscopy images.

“These things we tend to think of as being kind of ugly and want to hide — mold spores and mildew growing in our bathtub, and bacterial colonies that are on all the surfaces of your house — they’re all noncharismatic animals, but they’re really crucial to our lives.”