Ok lets see if I can help you.
I don't use Outlook express but it's on my PC and I looked at it. Open Outlook express and go to tools, options. Click on the sent tab. See the mail senting format put a check in the HTML box.
Then click on New Message and go to format and put a check by rich text (HTML) and sent pictures with attachments.
There setting above are for senting email.
This here is from the Outlook express help.
To view a file attachment
In the preview pane, click the paper clip icon in the message header, and then click the file name.
-or-
At the top of the message window, double-click the file attachment icon in the message header.
Tips
To save a file attachment, click the File menu, point to Save Attachments, and then click the file name. To save the attachment from the preview pane, click the paperclip icon, and then select Save Attachments.
When a message has a file attached to it, a paper clip is displayed next to it in the message list.
Maybe someone that uses and know more about Outlook express can try and help you because you should be able to see a .jpg file.
Now you could go here to
http://www.irfanview.com/english.htm and get IrfanView and it will let you view many image types. It's also free.