Your detail image should be able to stand alone on its own merits.
No matter what aspect of the work you are choosing to place at center stage, the detail shot should be visually compelling, and well designed. Ideally, a good detail image is also a superb composition with great colors, and formal pictorial qualities. Think of all the formal properties of a good painting. The detail image should be an eye-catching image that exists independently of the full view shot, even if it is not projected.
Details should always offer as much information as possible about the work.
Consider in advance the fundamentally important or unique features of your work (never forgetting the impact of a thoughtful and carefully arranged composition). The close-up should expand on the information given in the full view image and further define the particular character of the piece. Featured details of surface, functionality, or special technique should always be viewed in that context. If the conceptual content is an important aspect of the work, then the detail should somehow address that issue.
Your close-up should also be considered a companion image to your full view.
In many circumstances, only two images for each piece will be sent to the jury, a full view and a close-up. This combination should be a fantastic "one-two punch" offering a lot of straight forward information. Although there are no guarantees that your detail and full view shot will be shown together, you can increase the likelihood that they will be by placing your images adjacent to each other in a digital format. Additionally, be sure to clearly label on both image and paperwork that this is a detail of the full view.
Details shown should be relative to the size of the work.
The detail for a small piece of jewelry is going to show half the piece or even less with very little or no background. An artwork that is five feet tall might have a close-up that shows about 12".
The camera "sees" all details as being equal.
In contrast, human vision establishes a hierarchy in what it sees, often assigning greater visual weight to a focal point in the work. The camera does no such thing. Consequently, flaws, shoddy craftsmanship and unintended imperfections are depicted with the same visual weight as everything else. This, of course, is distracting and will immediately turn off a knowledgeable juror, critic or curator.
Details must be crisp, clean and in focus.
Close-ups of small objects or jewelry are especially difficult and present many problems for the photographer. General-purpose camera lenses usually do not have a focal range for close-up (macro) photography. Some cameras may be able to use macro lenses or extension tubes (a less expensive alternative), but if your camera will not focus on your detail, do not take the picture. A bad detail can become more of a hindrance than an advantage. Your chances of being chosen are greatly diminished by including a bad close-up.
Creating a close-up image with Photoshop from your large view digital image is possible, but may not produce the best close-up.
Framing the shot and lighting the artwork is extremely important. The staging required to produce a quality image for a full view shot can be quite different than for a detail shot. Trying to adapt one shot to serve two purposes most often yields poor results. In addition, when you Photoshop the image you don't want to reduce the size of the file (if you are intending to use the digital image for printing in books and magazines). If you are zooming in on a small portion of your digital image, make sure that you do not reduce the pixel resolution of the image.