Sorry for asking after such a long time,isn't there any way to add a thumbnail to replace the blue swirl galaxy ? Actually,the person for whom i made the thumbnail reverted to me after long time asking "can you try and see if there is any further way to show the thumbnail in the screen saver or make it look a little more professional ? " Also installing the screensaver on their Mac shows the security warning so i guess it would be solved by just signing the screensaver. I haven't signed any screensaver before so i have no idea. Let me know if there is any other steps apart from just enabling signing in Xcode.