Install one or more placeholder pictures. Again, there are many ways to do this. One quick way is to take random pictures using the phone camera and optionally rename them as appropriate.
In BitPim, Menu -> Data -> Get Phone Data ...
From the Get Data from Phone dialog, check on Wallpaper and click on OK. BitPim then retrieves the pictures from the phone.
Select a placeholder picture, invoke the context menu and select Replace.
From the File Selection dialog, select your custom picture file.
Depending on the format of your picture file, an Image Preview dialog may appear and allow you to convert, cut, and trim your picture into an JPEG clip. Click OK when you're satisfied with your clip. (To bypass this step, select Overwrite from the context menu instead).
The content of the placeholder picture will then be replaced with your new clip.
Repeat step 6 through 8 for other placeholder pictures.
When you're ready to send your custom pictures to the phone, click on Menu -> Data -> Send Phone Data ....
From the Send Data to Phone dialog, select Wallpaper and click OK. BitPim then sends the newly "replaced" pictures to the phone.
BitPim Online Help built 17 January 2010