In macOS 10.13 High Sierra, Apple removed all the iPod icons from the system, so whenever you restore your iPod, or simply set it up for the first time, it shows up on your Desktop looking like this:

Instead of looking like this:

The easy solution is to manually add an icon to your iPod, and here's how you're going to do it:

First download the icons, there are two versions: ZIP with multiple PNGs for Mac, and a single DLL file for Windows.

Open your desired PNG icon in Preview. On your keyboard press cmd + a  to select the image, then copy it to clipboard by pressing cmd + c. It should look like this:

Next, right click on your iPod and choose Get Info

Click on the drive icon in the top left so it lights up blue, then press cmd + v  on your keyboard.

The icon should now look like this:

All done! Close the window and enjoy your new iPod icon.