Well you can always send a message to set the should update view variable, which is in any UIView object. I forget the exact method call, but you can use XCode and CTRL-. to get a popup of all the methods available to call.
Or you could take a complete different approach where you use either KVO Key Value Observer pattern to the button when touched. Or you could have a UINotification sent and have all the images registered to receive that notification and then update themselves.
I have had buttons change the screens without ever having to send the message that UIView should redisplay. It happens automatically if you change the appearance of any UIView object on the UIScreen.
Yeah, looking at your code in your other post. If you just loop through your assets and call the checked method that you wrote that updates the UIView of that asset, then it should automatically update your screen.