There have been a lot of questions around how to create great looking icons like you see for the Microsoft apps in the Windows Mobile 6.5 Start screen. These icons aren’t icons at all in the traditional sense. Up until Windows Mobile 6.5, you could only use icon (.ICO) images embedded in the EXE file for your Start menu icon. The new Windows Mobile 6.5 Professional Start screen still uses these icons, but you may notice that they are scaled slightly. You may not notice any difference in the appearance of the icon, if you do, you can use a PNG file for your application icon. If fact, the Windows Marketplace for Mobile requires that you use a PNG for Windows Mobile 6.5 applications.
For details on now to specify a PNG file for your Start Screen icon see my blog post here.