It's kinda obvious that I don't... Most of my sprites are recolors/slightly modified. Ryu and Joe are the closest I have to fully origional, and they were made by Chromus.
All the sprites I made for my comic (see my website on TGB for the small number I made) and quite a few for Pez's comics were modifications of Mega-Man sprites (either a simple recolor, like Roscoe, or an extensive modification, like Dagron) provided by Sprites, Inc.
I know of a webcomic author who uses totally original sprites for his webcomic. You can check out his work here: http://squidi.net/
I made only one sprite, and she took me about a week to make. But I might make more because it was fun, even if my fingers get sore from clicking a whole lot.