In OS 4.2 you can choose the size of attached images from the Mail application

iOS iPad 4.2 to allow you to adjust the size (between a predefined sizes) of images that we will send through the Mail application

This very interesting new feature comes with the latest version of IOS and does almost transparent to the user, because, as you see in the picture below, the option is fully integrated into the Mail application interface.

Track | iPadevice