ANY type of files can be attached with the AnyAttach cydia tweak ($1.99) and a couple configuration adjustments in the settings menu. There is a separate section to browse your photo applications for any photos or videos, great for sending multiple images at the same time.
AnyAttach ($1.99, USD):
[Cydia Description] A tweak that enables you to attach arbitrary files to your emails right from inside MobileMail. It comes with a file and photo/video picker that is accessible via the paper clip button that will be added to the subject bar in the mail compose window. No icon will be added to your homescreen. Options can be configured from the Settings app.