Icons are also usual images, except they are in different format called ICO. You can use any image on the computer as icon by performing image to icon conversion. After conversion, you can use resultant ICO image as icon anywhere.
Free tool to create icon from image
Download ImagIcon free utility to convert any image into an icon. After the install, open the application and drag any image into application window.
Specific image will be converted into ICO icon format and saved in the same folder of the actual image.
It is a free utility and allows conversion of JPG, PNG, BMP images into ICO icon format.
Free Online tool to create icon from image
You can use free online tool ConvertICO to create icon from any image. Click browse to upload any PNG format image on the computer. This online tool will convert image into ICO icon format. Reverse conversion of ICO icon to PNG image is also possible.