Create your icon and make two copies. Name the first one 'Black_DataTypeLTE@2x.png' and the second one 'LockScreen_DataTypeLTE@2x.png'.
(If not already existing) Inside your XXXX.theme folder create a new folder 'Folders' and inside this one 'UIKit.framework'. Paste both icons in the latter one and re-apply your theme in WinterBoard.