Adding a set of background images with positioning

[Neo_Angelo]

Hi guys, i've seen on a few skins that they use a set of images to form a big background image to make the forums look either rounded or a variety of shapes, from like a curtain effect to whatever heres an example of what i mean: www.ifskinzone.net

my question to you is how do i add these background images and where should i edit the template and with what code to add them in.

to make it easier i have 6 different images:

top_left.gif
top_right.gif
righ_col.gif
left_col.gif
bot_right.gif
bot_felt.gif

when placed correctly will make my forums look like they are rounded etc and give the forums more depth.

now what i'm trying to edit is the background (MAIN CSS Body and Background) not the actual forums themselves.

since i know the CSS for positioning and such i have in my extra CSS:

topleft
{
background-image:url('/images/angelwhite/top_left.gif');
background-repeat:no-repeat;
background-attachment:fixed;
background-position:top left;
}

and the same for the other with their correct positions.

now i'm guessing i have to edit the forumhome template to make the background appear on everypage if not please correct me.

now this is where i get stuck, when i call the CSS nothing happens <style="topleft"> what am i doing wrong, or what code should i be using instead?

thanks in advance for the help.