Remove background from a few hundred images repost

We have 690 avatar images which need the backgrounds removing and saved to PNG format with Alpha transparency. The resulting files should be a small file size but without compromising on quality at all. We will supply the images, supplying a few to begin with to confirm quality, and if the quality is acceptable we will send the rest. We will be paying US 10c per image. Every image in each set will require our approval before payment will be made. Most images will be static, although a few are animated gifs. The gifs will need to use the first frame of the animation for the final image.