I’m afraid that you’ve been bitten by a bug. The gearwheel icon at the top right of the Now Playing screen brings up the Customize screen for turning the elements (Lyrics, Artist photo, etc) on or off.
The bug is that if you turn them all off, then the gearwheel icon disappears as well, and there is no way to get back to the Customize screen.
I’ve reported it to Support, but there doesn’t seem to be a workaround for this at the moment. I’m afraid we’ll have to wait until it gets fixed in a future release (I’ve been bitten by this bug as well).