To convert a JPEG to a desktop icon, first use an image editor or online converter to save the JPEG file as a .ico file. Ensure the icon is appropriately sized, such as 256×256 pixels.

You can set a dark or any icon of your choice – but the images have to me in the .ico format. Read: How to change File and Folder Icons. As an example, let us change the icon to a dark one.

You can repeat these steps with other ICO files to get different results. You can also change the taskbar color. Reverting ...