Tools Needed: * RT Seven Lite (Download it from here)

* Windows 7 operating system installer ISO or DVD (x86 or x64)

Step 1: Launch RT Seven Lite and select the operating system image you want to customize. (Click here if you don't know how to start with RT Seven Lite)

Step 2: Now enable Customization task in RT Seven Lite as you see in the screen-shot below

Step 3: Now go to Customization section and you can see "Screensaver, Themes, Wallpaper, Logon Screen, Gadgets, Documents, Sample Musics, Media Sounds and More Options" tabs as below in the screen-shot

Step 4: Click Screensaver tab in customization section and you can add screensaver files (.scr) by clicking "Add" button which must be less than 5MB. You can also set a screensaver as default by clicking "Set As Default" button. See the screenshot below

Step 4 (a) : Click Themes tab in customization section and you can add theme files (.theme and .themepack) by clicking "Add" button. You can also set a theme as default by clicking "Set As Default theme" button which will be loaded during first login. You can also set default window frame color (Sky, Twilight, Sea, Leaf, Lime, Sun, Pumpkin, Ruby, Fuchsia, Blush, Violet, Lavender, Taupe, Chocolate, Slate and Frost). See the screenshot below

Step 4 (B): Click Wallpaper tab in customization section and you can add wallpapers (.jpeg and .jpg) by clicking "Add" button. You can set a image as default by clicking "Set As Default desktop background" button. You can also set desktop wallpaper position (Center, Fill, Fit, Stretch and Tile). See the screenshot below

Step 5: Once you finished your selection and click "Apply" button at the bottom to change the settings and save the image.