The icons need to be done in a format they will be placed on the iphone app as 24x24 pixels, 48x48 pixels 57x57 and 104x104 pixels .
Original format needs to be illustrator vector format for scaling.
Please see the list of icon as sketches (attached file sketch_icons1.jpg). The icons they have to be in the illustration style shown (attached file sample_icons1.jpg).
Use colors that make the icon look more real, as an example the camera needs to be more light metallic color, etc. There is a style of 3d but not a 3d object.
The key is to make the icons easy to read and understand of what they do specially in the smaller size so feel free to simplify. As well as they have to be fun, and consistent with the audience.
Make sure the icons don't look static, they need to be in action and with an angle to float nicely on the interface.