Many mosaic materials are specific to where and how they will be used. For exterior public mosaics, especially on the ground, it is important to use color body porcelain tiles that can withstand both weather and use constraints. Color body tiles are not glazed, but have color throughout the tile and they are not slippery. So, for example, if a color body Dal or American Olean type tile is used and it gets chipped, the color does not change as the color is throughout the tile, not just a glaze on top.
Glazed wall tiles cannot be used outside in any location where there is the possibility of freeze-thaw conditions. Glazed wall tiles are for interior use. If they chip, the underlying color of the clay, either white or terra cotta, is revealed.
Even in Santa Barbara, where it rarely freezes, colorful beautiful wall tiles in an exterior area subject to intense heat will delaminate, ruining your mosaic.