1/ Keep it Small - Keep the size down to a maximum of 400 pixels wide. Smaller pictures upload faster and look better in your listing. Most digital cameras have a 1 Million Pixel or VGA setting. Use this for your eBaY images. But do remember to set it back afterwards!
2/ Make it Square! - Your eBaY galley picture will be presented (squashed) into a square. Remember this when you photograph your subject and your gallery images will look in proportion. If your subject really is too long and thin to make it square, consider adding text or background frame or maybe it's box to make it square.
but adding the box makes the picture square so...
3/ More is best - Include further images in your listing. Imagine you are buying the same item... Would you like to see it from the back or any part in closer detail?
Close up showing flexible LCD Screen on the Fuji S9500
4/ Avoid Flash with close up shots - If photographing small items or detail, try a shot without using the flash. Press 'Flash' button on camera until flash symbol appear to be crossed out. This will often give the picture a more natural appeal. Some camera's such as the new Fuji FinePix F and S series are capable of shooting without flash in almost no light at all without needing a tripod.
With Flash and Without...
5/ Beware of unwanted reflections or distracting backgrounds. Go for a plain background - need not be a professional backdrop - often some coloured card or white sheet will do.
Hmmm... Which camera is for sale?!
6/ Don't over-manipulate - Photo software is great but too many product shots are ruined by over editing and sharpening. This takes time and may cause buyer to be suspicious. Apart from cropping and colour correction, avoid spending too much of your time 'touching up' your photo.
Not the way to loose the reflection and where's that scratch gone?
Please... Never attempt to hide a defect in this way. - It will reflect in your feedback!