If you have used Gmail for any length of time you likely remember the options about displaying images. At present Gmail on the desktop lists the option as “display images below” and on a mobile device you see “show pictures.” But regardless of platform, the need to tap that link will soon be going away. This change will first be arriving on the desktop, and then later on Android devices.
First things first though, Google has said they did this in an effort to protect the user. Simply put, they were trying to protect you against unknown senders sharing images that could compromise your system. When receiving email from an unknown or untrusted sender the images would be off. Along with the option to display them, you could also opt to always display them when receiving an email from that sender.
Similarly, on a mobile device the wording was “always show pictures from this sender.” Regardless of the wording, it seems Google has found a way to present the images and still keep the user system safe. Moving forward Google will be serving all images after they have been run through a secure proxy server. This is as opposed to simply serving up the images direct from their original source.
Alternatively, those who either don’t trust those secure proxy servers from Google, or those who just like things they way they have been — there is an option available. Google has said they will provide a way for users to stick with the current setup. This can be done by heading into the settings (on the desktop) and looking for the “ask before displaying external images” option under the General tab in Settings.
Furthermore, Google has said this option will be default for those who previously selected “ask before displaying external content.” This is being rolled out to desktop users as of today and the mobile apps (including Android) in early 2014.
SOURCE: Official Gmail Blog