It is straightforward to change one of the icons provided by AdapTable with your own icon. Simply override the relevant icon in your css with your preferred image.
In this example we have supplied our own icons for the Export and Alert functions toolbars. We overrode the .ab-Icon--export and .ab-Icon--alert properties in our css with the new images. (See source code here).
We downloaded the new icons from the same Material Icons site used for the shipped icons, but they can come from anywhere you specify.