Update

Valve keeps deleting my controller configs whenever I mention in their description that they use custom icons. Plus, Tower Unite is an ever-evolving game that requires regular changes to the Steam Controller config to make the most of each of the games' updates. Because of this, I haven't been using custom icons for my Steam Controller configs for some time. Everything below is currently out of date. This might change in the future, though.

Steam Controller Icons

Steam Big Picture Mode allows you to set custom controller configurations for your Steam games. It supports multiple kinds of controllers, including Valve's own Steam Controller. Here you can download the custom icons I've made for these configs. Most of them will be for the Steam Controller, but configs for other controllers may be added on occasion.

After you've downloaded the compatible controller configuration in Steam Big Picture Mode, all you need to do to install these custom icons is copy the image files linked below and paste them into the same folder as the default Steam Controller icons. The folder directory may differ depending on where Steam is installed, but for most 64-Bit Windows users, it should look something like this:

"C:\Program Files (x86)\Steam\tenfoot\resource\images\library\controller\binding_icons\"