The short answer is yes. You can use two methods to achieve the result.
Method 1
Using an image editor, create your image sets with a name for each sidebox you want to change and save your graphics to includes/templates/CUSTOM/images/ and upload it to your server.
In your includes/languages/CUSTOM/english.php
find this line of code:
define('BOX_HEADING_CATEGORIES', 'Categories');
You can change it as follows:
define('BOX_HEADING_CATEGORIES', 'your_english_graphic.jpg');
Now in includes/modules/sideboxes/CUSTOM/categories.php
find this:
$title = BOX_HEADING_CATEGORIES;
and change it to:
$title = zen_image($template->get_template_dir(BOX_HEADING_CATEGORIES,
DIR_WS_TEMPLATE, $current_page_base,'images'). '/' . BOX_HEADING_CATEGORIES,
HEADER_ALT_TEXT);
Note: You would do this for each of your sideboxes.
Make the needed changes, save the files and upload to them to your server.
Method 2
If you want to replace the default Zen Cart™ background image (tile_back.jpg ) to be used for all the sideboxes use an image editor to create your image (using the same dimensions as tile_back.jpg ) and save it to includes/templates/CUSTOM/images/ and upload it to your server.
Now open you stylesheet.css
and find following:
.leftBoxHeading, {
margin: 0em;
background: url(../images/your_background_image.jpg) #FF6699;
padding: 0.5em 0.2em;
}
.rightBoxHeading {
margin: 0em;
background: url(../images/your_background_image.jpg) #FF6699;
padding: 0.2em 0em;
}
Change the image file name in each of the URL functions, save the stylesheet and upload both files to them to your server.