FYI: Larger pictures are available on eBay Item pages now. Because photos are so important, larger pictures are now available on Item pages.
The display size of the pictures at the top of listing pages has increased from 300 pixels on the longer side to 400 or 500 pixels (depending on the buyer's screen resolution). That's 25% more space to show your items.
Later this summer, the size of pictures displayed in the Enlarge and Zoom features will also increase to approximately 1000 pixels on the longer size.
