Please take a look at the Apple Icon Design Guidlines at http://developer.apple.com/library/…000967-TP6
I have developed an iPhone/iPad App called iPIN. The App is live since July 2011 and very successful in Europe … hopefully in the rest in the world as well in the future.
Originally the App has been designed to store PINs (Personal Identification Numbers) like the PIN of your credit card - hence the name of the App and the current "design" of the App Icon, which is very simple (cost one night and a bottle of red wine :-). Meanwhile, the user can store user account (login) information as well ... well, it's a simple but nice PIN and Password App and I'm planning new features to store any private information in the App.
At present I'm working on the Mac OS X Version of the App (the user can synchronize the data via iCloud) and I’m looking for a very nice, creative App Icon for the Mac OS X platform.
The Mac icon can be similar to the iPhone/iPad Icon - but I'm completely open to new ideas - also to change the icon of the iPhone/iPad version.
There are a lot of Passwords Apps available at the Apple App Store. Many use icons with a key, a lock or a safe. If possible, the icon should differ … or you have really a perfect idea to combine these symbols with the name of the App.
I’m not a marketing professional - but I love clear and elegant designs. Like the App tries to fulfill the Keep-It-Simple-And-Secure (KISS) principal, the App icon should suggest the same: it should be clear, simple and elegant without “bells and whistles”.