The following code will let you use featured images as thumbnails in your custom menus. Paste this in your child theme functions.php file, or theme settings > Advanced > User-defined code:
atom()->setContextArgs(‘primary_menu’, array(‘walker’ => new ThumbMenuWalker()));
class ThumbMenuWalker [...]
This is a short walktrough on how to let your website users upload their own avatars, without using a plugin.
First, define the maximum image sizes (note that we will only downsize, smaller images will get browser-resized):