V1.39
Downloaded and installed per the instructions.

After unzipping the files on your computer, follow the folder tree to /your_template/. Rename the /your_template/ folder to the folder name of the custom template you are using.

Done.
After making the folder edit, ftp the /includes/ folder to the root of your store on the server. The files will automatically be placed in the correct locations.
Since my site has not ye been uploaded yet I saved the /includes/ folder in the root directory (Zencart)*Note*: If you have modified tpl_main_page.php, remove the copy from this package and merge the code line described below into your existing custom copy.
To be honest, I don't recall having made any changes but I copied the tpl_main_page.php and merged the code by a simple cut and paste.
Next:
To use different backgrounds (in any desired page element) for each category or page:
Name your background images like smartbg_23.gif or smartbg_shippinginfo.gif and save in /includes/templates/your_template/images/.
Done renamed a pic to smartbg_stuff.jpg

To switch backgrounds for a top category and all its subcats, add its id like _# to smartbg.
To switch backgrounds for a single subcategory, add its cPath like _#_# to smartbg.
To switch backgrounds for all ez-pages, add _page to smartbg.
To switch backgrounds for a single ez-page, add its id like _page# to smartbg.
To switch backgrounds for a particular Zen Cart page, add its name like _pagename to smartbg. Done. pic now named smartbg_page#2_stuff.jpg
Look in the address bar to get the current page name, ez-page id or cPath.
Combine the smartBG_ class with the class or id of the element you want to affect, per the stylesheet examples below.

In /includes/templates/your_template/common/tpl_main_page.php, this line


<body id="<?php echo $body_id . 'Body'; ?>"<?php if($zv_onload !='') echo ' onload="'.$zv_onload.'"'; ?>>

is replaced with

<body id="<?php echo $body_id . 'Body'; ?>" class="smartBG<?php echo smart_backgrounds();?>"<?php if($zv_onload !='') echo ' onload="'.$zv_onload.'"'; ?>>

If you want to use jpg or png images instead of gifs, change echo smart_backgrounds() to echo smart_backgrounds('.jpg') or '.png', etc. Done, changed to use .jpg

No change to pages 2,3, or 4. all still have the same background as the main page.


To clarify what I'm trying to do.
I'd like to have a diffrent pic as a background for every page. I've already gone into the my Stylesheet and used the /* */ do-dad's* to allow my pic to be visible.

* This should let you know that I'm not an IT guy, a computer guru, programmer, etc.

So K.I.S.S. !!