To change your avatar, please follow these steps: 

-Click on the commander avatar on the top left of the screen.
-Clicking on the round arrows in the top right of your current Avatar.
-You can either choose one of the available officer avatars or uploading an image directly from your device. (simply keep sliding the officer avatars to find this option)
-Click on change avatar, and the "Change Avatar" item will be used from your backpack; if you do not have the item, you can change your avatar with the cost of 400 gold.

*Please note that the feature to upload a personal image from the storage is unavailable on some devices.