Hi my client was need of creating themes like this http://mappn.com/community/index.php?topic=42.0
I have no clue where to start with. when I googled it I just get themes for style/theme for aplication.
Can anyone suggest where to start learning customizing themes for android phones. plz share if u find any opensource.
The default Android home screen is not themeable, so you will either need to write your own replacement home screen, or write a theme for one of the existing home screen replacements that others have written and support their own custom themes. Not all are free, and not all support themes.
I don't know much about writing your own Android home screen, other than a home screen activity should respond to the android.intent.category.HOME category in its intent filter (About intent filters).
You have to look at framework-res.apk - most modding is done there. Normaly you find it at /system/framework/framework-res.apk. You can open it with Winrar or 7-Zip and take a look at all the ressources in there.
For more just google it :)
edit: a starting link