When creating the UI for the BlackBerry 7100t (for T-Mobile) I created the icons and interface on the left. They liked the icons and the rollovers, but they wanted something almost "photographic". So I created the interface on the right.
I created the left icons in Adobe Illustrator and made a model in Photoshop. This allowed me to export a mock-up of the interface in HTML and show the team how it would look on the phone.
When I made the interface and icons on the right, I created several versions of each icon and the team picked which they wanted.