How many pictures can be stored on a 2gb sd card?

It all depends on what type of camera you use or what type of photo you save. If your camera is lets say 5 mega pixels, we would do 5x3=15. The three come from the three colors in any picture on you screen. In total the image would round up to 15MB size.

Do note that images can be compressed into smaller sizes but later on you would have to uncompress them.