what image location for root directory ?

The best way to go: the theme directory should have its own images subdirectory.
E.g. if you distribute a theme called “ultimate” ?? – you should have a directory ultimate containing all the necessary files [index, archives, header etc.] AND a subdirectory “images” with all the images used in the theme. And you’ll have to include the images, too, in the distro zip.

I think you didnt get it .
Yes im asking that only .i have a image folder under the directory. but I need to know how to call it in CSS. say an image my-theme/images/myimage.jpg

now what should I give in “my-theme/css.css” so that it`ll call “my-theme/images/myimage.jpg” .

I think you didnt get it .
Yes im asking that only .i have a image folder under the directory. but I need to know how to call it in CSS. say an image my-theme/images/myimage.jpg

now what should I give in “my-theme/css.css” so that it`ll call “my-theme/images/myimage.jpg” .

The css pulls images relative to where style.css is so you would use just url(images/myimage.jpg); if the images directory is a subdirectory of where your style.css is (a pete and repeat sentence to match your double post :-).