Most frequently issues loading photos are a results of connection issues. If you're working on an internet connection that's experiencing slowness the operation may time out before the file is able to fully load.
Here are a few tips to ensure your images upload properly to your listing:
-- Images should be a minimum of 570 pixels wide, and ideally no larger than 1000 pixels wide. They should be around 300k in file size or smaller. Files larger than this may time out, especially on a slower Internet connection.
-- Make sure your images are converted to sRGB before uploading to ensure that the colors you see on the site match the originals. CMYK color profile is for print only. Also, make sure the file is a properly encoded jpeg, gif, or png.
-- Do not upload untouched files pulled directly from your digital camera. Make sure to save them using an image editing software, such as Photoshop or Paint. Many cameras save their images in non-standard jpeg formats that don't work with Internet applications. If you save them for the web using image editing software, they'll be put in standard jpeg format.
After ensuring your uploading a photo of appropriate size, if you're still having difficulty I would suggest closing out your browser, restarting your computer, and rebooting your router. This can establish a new (and ideally better) connection to your internet service provider.