A good way to clean shower tiles naturally is to use vinegar and water mixed in a spray bottle.
Mix a 50/50 solution of water and vinegar into a spray bottle and shake it up.
Then spray the shower tile with the vinegar and water and let it sit for a few minutes and then scrub the shower tiles with a scrub brush or sponge.
If the shower tile is really dirty and hard to clean then you can mix some baking soda and water together to make a baking soda cleaning paste.
Then use a sponge to put the baking soda paste onto the shower tiles and use the sponge or a scrub brush to scrub the shower tiles.
Then just use the shower to spray it off if you have a handheld shower head.
You can also turn the shower on to a hot enough temperature and allow it to steam for 10 minutes or so and then the steam can help remove the grime from the shower tiles.
You can also buy some tile and grout cleaner at Walmart or other stores and even use a toothbrush to clean the tile grout.
A steam cleaner that you put water in and then plug it in also helps to steam the shower tiles clean.