When you right click on the filename is there no option to choose which program you open them with ? Normally choose Paint or Windows Picture and Fax Viewer.
If necessary start Paint separately and select the file you want to view.
Or is the problem that you can't find where the JPG files have downloaded to.
I have two different sources for opening my e-mail accounts as I have have two different accounts; One is AT&T through Opera and the other one is hotmail account through Internet explorer. Through Internet Explorer, when I click on to open the e-mail that has a jpg file attached, I can get the message, but for the jpg files, I get a big gray square. Unable to download or bring the jpg into view. My AT&T account through Opera, I get the e-mail message, a postage stamp view of the file, then for the large file, there is a big gray square.
With Hotmail you normally have to opt for pictures to be displayed -- examine the Hotmail screen when you open an e-mail.
I use Opera and I have no problems downloading pictures which are usually listed as attachements by file name within my Yahoo Mail screen. Once downloaded they normally open using Windows Picture & Fax Viewer.
Sometimes pictures embedded in emails don't display but I can usually download them . I don't think this is an issue particular to Opera -- or IE -- I think it varies with the originator.
Incidentally, there is no reason to use a different browser for each e-mail account.