Creative Commons and other 85,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
The image is of a closed circle. Inside the circle are two letters. The letters are capitalized Cs. They are side by side but not touching each other. The Cs are also not touching any part of the circle's edge.