How to set wdf file? I want to display it's background my picture.

Here you got a template:

WINDOW WINSTART
{
TITLE "Your Game Name";
SIZE 380,200;
MODE IMAGE;
PICTURE <starter.bmp>,OPAQUE,0,0;
PROGRESS RGB(0,0,255), 200, 0, 190, 380, 10;
}

starter.bmp is a 8-bit bitmap.

Edit: And you should update to version 6.6

If he can
Or...

I doubt it

...too...