It depends on what OS you have on your BB. If you are using 4.5 you can do so by Going to Email --> Options --> Email Settings --> then set the Download Images Automatically to Yes
Task 2: Set the Download Images Automatically option (Set this option for each integrated email account)
1. On the BlackBerry smartphone, open the message list.
2. Display the menu and select Options.
3. Click Email Settings.
4. In the Enable HTML Email section, click Download Images Automatically and select one of the following:
* Yes, to automatically retrieve embedded images
* No, to manually download embedded images