For example, someone wants to be anonymous and created a dummy Yahoo e-mail account, now he wants to send an image over the newly created email via Tor. Does this protect his anonymity? Can you someone be traced by attaching an image to emails delivered via Tor? What alternatives does he have?
Safe in what way? Anonymous? The person is using Yahoo firstly with their already record-breaking feat of having the largest leak of data beaten by themselves recently. Secondly the picture itself has metadata attached. Thirdly they are sending it over an email and one that is not a secure one as highlighted by the first point. So basically, no, it isnt safe if they are attempting to be anonymous. Using Tor while giving information on a known link is not anonymous. All that happens is the IP address shows as different, but as mentioned, they are using Yahoo, let alone a common email. May as well use a megaphone and a movie cinema.
For a part of the question, here is the answer.
With an email account, if you right-click on an open email you have received, you can see some of the information that is collected and gathered based on your email account.
As for the picture, if you right click on the image, you can see the metadata attached to it. Some metadata gives your location as a gps location, as well as date and time, which could pinpoint you to a specific place, time or event.
To view the metadata on your picture, one program is Darktable, which is an image editing platform. I cant share with you any alternatives as for all I know it could be a CP image or something similar and I want no part of that. Sorry if it isn't. I'm stuck between helping and caring, but helping and caring about who as my first priority.