Unless someone intercepts your email by hacking your computer or account then the image you send them will only be viewable to them. Personal email is personal, not public.
Email logs may be maintained by hosts through which the messages travel. These logs may have the names of the attachment files and sizes. It is very difficult to be on a network without leaving some trace of activity. The pictures may not be able to be read but the fact you sent something to someone may be traced along the path between the source and destination.
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