I emailed the dev this exact question a couple of weeks ago, it is possible, open the app, the first page you see with the big icons press the applications one, then scroll to the app you want to change the icon of and press, up the top left it then says change icon, press that then navigate to where ever it is you have the icons you want to change to, simple really but i couldnt see it for the life of me. Always try the dev first, its worked countless times for me if i cant find an answer with el Goog