itch.io

Typically a graphical style where there are one two colors. (A bit can be either on or off, so two options) Commonly black and white, but can be any combination depending on the style the creator is trying to accomplish. 

Graphics for creating characters

PNG, or Portable Network Graphics is a common image file format that is lossless, can contain an transparency channel, and compressed. An ideal format for distributing static assets without any loss in quality.