A shelving system for my bathroom that uses 12mm square steel tube for the vertical standards. 5/16-18 threaded studs anchor the top and bottoms of the tubes to frames on the ceiling and floor (a sliding cabinet,) they support the shelf loads primarily in tension.
The shelves below are 22mm thick, solid Cypress wood from our property, and the shelves above are a mix of cellular polycarbonate (greenhouse) panels at 10mm, painted aluminum channel and cypress supports.
