Step 1: Login into your cPanel.
Step 2: Go to the File Manager. Select your osCommerce installation directory and click Go.
Step 3: Upload your background.png background image to the images folder in your osCommerce installation directory.
Step 4: Edit the stylesheet.css file in your osCommerce root directory.
Step 5: Now we will add the code to the CSS that will display the background image and change the background color to #fff8e5. The “body” CSS code is what will be edited.
Step 7: Change the following code:
background: #fff;
Step 8: To the following code:
background: repeat-x top url(‘images/background.png’) #fff8e5;
Step 9: Save the file.