To provide a nicer user experience in v1.2.4 the icon specified for an App tile is now deployed automatically and displayed in an App Center tile in both desktop and Web. Note that the minimum optimum size for an App tile icon is 96x96.

Due to the changes in the way the App Center is rendered you will need to re-deploy your Web Apps so that the icons are deployed.

These tile icons are also active in the new "Page Center".

You can copy your icons into the library directory (just drag and drop) and then reference them in the App "Settings" for the tile like this lib:/iconname.png