The first I am going to review is through the use of a free app called the Iconian. It is a free download for both Windows and Mac. It's so easy to use. There are a number of icon sets to choose from as well as colors, backgrounds, and styles. Once finished, download the icons you have made in Iconian and then upload them to Thinglink. Any icons you add to Thinglink will be at the top of your icon selections and ready to use.