The quality of the pictures on your products depends on the quality of the pictures you upload.
Picture quality is determined by resolution and compression.
Each has different trade off's between file size and quality. These files have no loss of quality, but the file size is by far the largest. GIF - GIF's reduce the color depth to a maximum of 256 colors to compress the size of the file. For photos, the human eye cannot tell the subtle changes in color, but along straight edges and in pictures with large solid colors, distortion becomes very apparent. To the left you can see differences between JPG and GIF formats.