Remote Viewer (like TeamViewer) with Special Requirement...

Hi. I'm making a Remote Administration Tool with a system of Parental Control with a Remote Screen Viewer for see what the user is doing and also can control their computer (keyboard and Clicks). Now I need add a special requirement. I need block the user screen and show to user a image (a warning image) but at same time when the user is blocked the screen/desktop and seeing the image, I want continue controlling their PC with clicks and keyboards. I dont know is this is possible but I saw some examples in youtube of users that can do it, but I dont find how. Any way PLEASE send me specific proposal of what you can do or some ideas for so this task, If you send me good proposal I will chat with you as soon as possible. Thanks !