Many abstract images are captured from close to a subject, perhaps revealing the fine detail of a surface. Such images may lack depth and hence become flat and consequently rather uninteresting two-dimensional pictures.
Many subjects can be revealed in a more rewarding manner by careful choice of viewpoint and the use of side lighting. Try to incorporate a range of camera-to-subject distances within the frame, ideally including features that can be compared and hence give the viewer a sense of depth. For instance, when photographing a range of similar but different coloured items, try positioning one of the items significantly closer to the camera. The similarity between the near and far items will be obvious to the viewer, and hence used as a measure of distance from the camera. This brings an element of depth to an otherwise flat image.
One of the problems associated with the approach described above is caused by limited depth of field. It may be impossible to render both the near and far items in sharp focus. This problem can be overcome by panning the camera relative to subject, so blurring the image in a particular direction and masking the depth of field problem. A similar effect can be achieved by using Photoshop to introduce motion blur in the desired plane.