Sure you can suction cup a waterproof Bluetooth speaker to your tile...and hope that it doesn't dislodge and whack you right in that tender spot on the downslope of your foot at the height of "Raining Blood." Or you can check out the H2OVibe, a speaker just as waterproof and just as Bluetooth-connected as other models, with the additional advantage of snapping right into its accompanying showerhead.
The H2OVibe Bluetooth speaker has a magnetic attachment for securing it in the center of the waterfall system overhead, and then removing for charging. Average playback time per charge is around 7 hours, with an LED reference light on the front of the speaker indicating when the battery is low (as well as when it's in Bluetooth pairing mode and when there's audio input from a Bluetooth device.) The speaker can pair with any Bluetooth compatible device at a distance of up to 33 feet.
For its part, the H2OVibe showerhead promises to rain down at 3 times the power of a standard showerhead. Installation shouldn't take more than a few minutes.