http://www.passionemac.com/macbookpro-icon/
MacBookPro – Display icons changed were too large – how can I get the screen back to normal?
Change Resolution Display: 1. Open System Preferences (either from the Dock or the Apple menu). 2. Open the Displays Panel and select the Display tab. 3. To the left of the tab displays You can select one of the resolutions of the list. Higher resolutions let you see more "stuff". Recommending at least 1024×768 unless you have a reason practical to use a lower resolution. 4. Exit or close the System Preferences when done.
Change Icons On Macbook Pro