The number of pictures that can be stored on an eight gigabyte iPhone also depends on the size of the picture. If the picture was taken by the camera on the iPhone itself, the picture will be two megabytes. Therefore, if you had no other data on your phone, and only wanted to store photographs taken with the iPhone camera, you could store 4,000 photographs on an eight gigabyte iPhone.
However, if you wanted to store photographs on your iPhone that were taken, for example, on a digital camera or with a webcam on your computer, this number will be dramatically reduced. Depending on the quality of your camera and the size of the picture, the photos could take up anything from two megabytes to 10, 15, 20, even 100 megabytes.
If you're finding that your current iPhone does not have enough space for all of your pictures, then there are a couple of options for you to take. Firstly, you could go through and delete pictures on your iPhone which you don't want or need. Maybe you've got a drunken shot of the back of a taxi from your night out last Saturday? You don't need it, so it can go. Duplicates should be deleted, as should different versions, for example if you edit your photos, you don't really need to keep the original one. If this does not free up enough space, maybe you should consider buying a phone with a larger memory.