Have you considered whether there's something that another company could do to limit the success of your app/service? In Stuart Hall's case, it wasn't the end of the world as this app isn't at the core of his business, but it's worth thinking about your own apps in this way.
Looking for device images for your marketing materials? Of course, if you only care about iOS devices you've got the marketing resources from Apple, but what if you want an Android device, or a laptop, or a Nokia C300? Facebook have a great set of imagery here. Just read the disclaimer before you jump in.
Note: I believe these have been available for a while but they got an update this week with more devices.