eBay now requires a minimum length of 500 pixels for the longest side; setting your camera's default to High or Medium picture quality will ensure your pictures are large enough. For the best possible display of your listing on all eBay pages, take pictures with a 1600-pixel dimension on the longest side.
Not sure how big your pictures are? Watch this short demo on determining picture pixel size.

Borders are not allowed on any of your photos. The only exception is if you have a 'natural' border created by photographing your square or rectangular item against a neutral-colored backdrop. This is often done with stamps or other paper items to call attention to flaws that may exist. In this instance, the visible edges of the background may give the appearance of a border.
Do photograph your item against a solid background without a border.
Don't use borders of any kind as a general rule.
Watermarks are allowed for ownership and attribution, but not for marketing information such as specific details about your item or customer service. Your watermark should be no bigger than 5% of the total image area, have an opacity of no more than 50%, and never obscure the item. Links are not allowed in watermarks.
eBay offers a watermark creation service as part of the listing process. You'll find it in the "Bring your item to life with pictures" section of the listing form. Click on the "Add or remove options" link. Use this handy tool to ensure your watermarks are compliant.
Do put your watermark outside of the main image area, at an opacity that doesn't obscure the image or is bigger than 5% of the total image size.
Don't place a watermark over the main part of the image, or use a watermark that exceeds 5% of the total image size.
Do include photo ownership or attribution copy in your watermark.
Don't put logos or marketing copy in your watermark.
No text or artwork (such as "Free shipping" or seller logos) may be added to photos. Copy that is essential to your listing should be placed in the title, subtitle, or item description.
Do use photos that showcase your item and nothing else.
Don't add text or artwork to your images.
Do include details about your listing—but only in the item description or listing subtitle.
Don't include logos and/or marketing text in your photos.
Listings without accompanying photos will no longer be allowed; every listing must have at least one photo. If your item isn't something you can photograph yourself (e.g. a vacation package), browse the Internet for free pictures without a copyright you can use with your listing.
Stock photos may no longer be used as the primary photo for a used item listing. Catalog images are acceptable, but not as the primary photo for non-new items; exceptions are the Books, Movies, Music, and Video Game categories. Video Game Consoles, however, must adhere to the new requirement.