It appears that some of the rear cover options for the Moto X 2016 (which may also be known as the Moto Z) have appeared online. These apparent "MotoMod" style modifications offer covers with a number of different designs and materials for Motorola's next phone. Materials for these covers seem to include leather and wood.
Images of these covers come by way of +hellomotoHK:
In addition to these style modifications, the Moto X will reported feature support for modular attachments such as speakers, a projector, and a full external camera. The Moto X 2016 is expected to be unveiled next week during the Lenovo Tech World event on June 9.