The BEST solution to this problem is to decide right away if you want to keep the image and download it to your computer. You can keep all of your photos in your Pictures folder on your computer, or use the program already on your computer to organize them (Windows has Windows Photo Gallery, Mac has Photos) OR you can download a program that will help you organize them. Many people like Picasa and it is a free download. Another program is Flickr and there are many others. But that is when you are downloading your pictures one at a time....
If you have NOT been downloading them one at a time and have multiple photos in various email messages sitting in your email program there is hope. It will take a while, but probably less time than it would take you to open each of your messages and download each photo one by one.
Set up Thunderbird to be your email client. It will most likely ask for your email address and password and automatically connect to your server and set things up so that your mail will download. If it does not work try closing the program and opening it up again. Depending on how much mail you have saved in your account it could take a while for all of the mail to download.
Next in Thunderbird find the place where you can download add ons. There is an addon called Attachment Extractor that will extract attachments from your email and put it into a folder on your computer. Find the extension and click to download it. You will have to restart the Thunderbird program before using it.
Next, go to All Mail. In GMAIL type 'has:attachment' in the search box at the top. Other email programs may have a place to click on a paperclip that brings all of the mail with attachments to the top.