Hi I just bought a 3650 today and really hate the layout and the way you choose menus.
Anyway I have taken pictures but how the hell do I save them as a background I can't do it HELP PLEASE !!!!
Take a look in the manual for the phone.
Save the picture in default folder, Select Menu->Tools->Settings->Standby
(I am translating a Danish menu, menu labels may vary)
Select the menu item 'background picture', confirm 'YES' and you have the dialog for inserting a picture.
Not quite intuitive, but it works :-)