From Forum Nokia Wiki

One of the most popular phone model today is the Series 60. To make a Series 60 theme just download this free tool:

http://www.forum.nokia.com/Tools_Docs_and_Code/Tools/IDEs/Carbide.ui/

--> After downloading the 136MB installer file, install it on your computer. After that click the “Carbide.ui S60 Theme Edition” from your program files. At first use it will ask for the directory where you want to save your work:

--> You may put any directory for the workspace. After that it will open the Carbide welcome screen where you can choose tasks like “Create Theme” or open an existing theme:

--> Choose “Create Theme”, it will open a dialog window that will ask for the name of the theme:

--> After clicking “Finish” the theme editor will appear:

--> To start editing background pictures, you will need to set the bitmap editor on the Preferences panel :

Note that the Bitmap Editor could be any photo editing software.If you have Adobe Photoshop then you can put it on the path of the Bitmap editor instead of mspaint.You can always change this to any exe file you want.

--> To start editing the background picture click Background > Idle Background > Convert and Edit in Bitmap Editor:

--> It will ask for the size of the picture/bitmap file:

--> Change the dimensions of the picture as needed. This is set to default (240X320) for Nokia Series 60 phones. Click OK to continue editing the bitmap/picture file.

MSPaint (or any bitmap editor you set) should open and let you edit as an ordinary picture file:

--> From this point, it is all photo editing creativity and making the background picture that you want to appear on your phone. Save the file to have it updated on the theme editor.

--> The beauty of the theme editor is that every item on the theme is editable using the same method. For example, editing the contacts icon is done by clicking the contacts icon and exporting the icon to a bitmap editor:

--> To edit each individual interface (i.e. Applications menu, Idle menu) use the Gallery Tab and click on the menu you want to edit:

On the above example, I clicked the Applications Grid 1 to edit the Applications menu of type 1.

(Note: There is a type 2 Applications menu on Nokia Series 60 )

--> After editing the colors and background pictures, export the file so you can install it on your phone:

--> It will ask for the location where you want your theme file be saved:

To put the theme file on your phone just send the theme to your phone via Bluetooth. Open the file in your phone’s inbox and just install it like an ordinary application. If you don’t have Bluetooth, you can put the file in your memory card using a memory card reader.

Best of Luck!....