I think google just made their clock app available yesterday on the google play store. Along with the built in functionality of the Google Clock (Alarms, Stop Watch and timer), it also ads a daydream clock that I think will fit what you want.
allows for a large digital or analogue clockface on your phone and has a "night mode" option to dim it to the lowest possible setting. if you dont enable "night mode" it'll stay at your phones display brightness.