The preferred file format for Premium Icons is SVG. We are finding that customers are not downloading or buying PNG icons. We will accept PNG icon in special circumstances such as highly-rendered 3D icons but, in general, we no longer accept PNG icons in most cases. When you upload SVG files, we will convert them to PNG as well as ICNS, ICO, CSH, AI and IconJar. Read more about SVG
What size icons do you support?
Most icons are designed in increments of 8 pixel sizes, but we have no restrictions on the sizes of the actual icons.
But you can download the startup icon templates for Adobe Illustrator