Cleaning mosaic tiles
Warm soapy water with a soft lint-free cloth or sponge. Do not use anything abrasive that could scratch the mosaic tile, this particularly applies to stainless steel mosaic tiles.
Note: on copper mosaic tiles soaps and other cleaning agents will accelerate oxidisation/patina, though depending on taste the aged copper appearance is desirable. Otherwise a cleaner like Brasso will polish them up.