[Q] Making custom icons for MIUI (for apps not in the market)

download an app called quick system info pro (free)
click all
find app and click on it
click details
the process name is what you need
Or launch the app you wish to get the process name for then go to Settings > Application > Manage Applications > Running > (hit menu) Show cached processes > click on the relevant app.

About half way down the screen you should see the process name.