Big Ben and other 65,000 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 icon has a square with a circle in the middle and inside the circle are two lines that slightly resemble a L shape. Above the square is a semi-triangle shape with the top missing, above that is a rectangle, on top of that is a triangle. Two lines are located at the bottom of the square at either end.