This instruction will change your original keyboard into Storm Keyboard (BlackBerry Storm Keyboard) only. However, if you would like to custom your whole theme, you can check out my post on how to turn you iPhone into BlackBerry Storm using PerfectStorm.

Your iPhone should be unlocked/jailbroken in order to use WinterBoard. Winterboard on iPhone (like its predecessor Summerboard for iPhone 1.1.4) is an iPhone theme manager that allows you to change any WinterBoard/SummerBoard theme on iPhone. See instruction on how to install WinterBoard via Cydia.

Install Storm Keyboard Via Cydia

Launch Cydia > Select “sections” at haptic menu > Select “Themes (Keyboard)” category > and select “Storm Keyboard” or you can tap “Search” in Cydia and type “Storm Keyboard” > Select “install” button at the right top and confirm it to install.

Activate Perfect Storm Theme via WinterBoard

Your theme still in the “unactive” condition. To activate it, just launch Winterboard and select “Storm Keyboard”. Your WinterBoard will verify with mark symbol. Press "Home" button and you’ll then bring back to the locked screen. Unlock it and you’ll see a fresh new look of your iPhone.