It really depends on how often those pictures are accessed. You could have thousands of pictures taking up gigabytes of space, but if someone only looks at one picture every other day, then it will use virtually no bandwidth. On the other hand, a single 50kB picture that was accessed a million times a day could easily bring down your entire line. The thing to keep in mind is that when someone wants to look at a picture, your server has to send it to them, and if 100 people look at the same picture, it has to be sent out 100 times.