What things affect the image of a pinhole camera?

An image made with a pinhole camera can first of all be affected by how much light the paper is exposed to. The longer you keep the hole of the camera uncovered, the more the light will reach the paper, thus affecting how much of an image will be created. If you expose the paper too briefly, the paper might not get exposed enough and as a result when you try to develop the picture there will either be no image or a very faint one. However, if you expose the paper for too long, the image could end up too dark.

If there are any areas where light can leak through the camera, that can result in the image being ruined and turning black.

The size of the hole might also affect the image. If the hole is not quite big enough, there will not be sufficient light for the paper to be exposed and an image formed. Make sure that the hole is just the right size (the size of the tip of a pin).