Some web servers are configured to limit the size of files you upload or have not enough memory for large image's dimensions size (width/height) processing. Both related to your server configuration. Web server configurations should be handled by your hosting tech support, so we recommend asking your host to fix this limit for you (upload_max_filesize, post_max_size). Try contacting them, and ask if they can increase two limits for your server PHP configuration and they should know what to do. Image processing and manipulation can eat up the server memory. You have to decrease image size before upload or increase server memory. In most cases for good looking products 1500px*1500px images usually are more than enough for any kinds of stores. To speed up your web store pages loading AbanteCart will create a bunch of smaller images for different pages like listings or basket page.