I have downloaded some images from an email using my gmail app . I tried to find it in my gallery and also in my storage but i couldn't find it either in my gallery or in my storage
In your Gmail app go to settings, then click on your your target email address (where you want to get image attachments downloaded) , then untick the option which says "Auto download attachment to recent messages via Wi-Fi" try again to get your image.
It seems attachment downloads are restricted to wi-fi (default) but option is not clear at all as it seems to imlply a different thing. So disabling this option implies both data and wi-fi are considered (although the option is a bit misleading) It however fixed the issue.
Downloaded images are saved in downloads folder of sdcard or here