If images in the Magento backend are not visible after a successful upload, while they are displayed without any problems in the frontend of the online shop, this may be due to the PHP configuration of the shop server.
This is because displaying an image in the Magento admin area requires allow_url_fopen, which is disabled or set to "false" by default on some servers for security reasons. If you follow the image link without allow_url_fopen being enabled, you will receive a "There has been an error processing your request" error with the message "Unsupported image format.". Seen with Magento 1.7.0.2.
