Sometimes the Black Screen of Death can spell doom for your re-booting computer. But if you don't have the flashy cursor and you are giving a PowerPoint presentation, the Black Screen can be your friend.
You don't have to have something on the screen all the time. I will say it again, you don't have to always project something. The power of your images comes when they integrate with your message to amplify the total content. If you leave up a picture after the point has passed you weaken the impact of the point you just made and the point that you will be making.
You can either insert a blank, black backgrounded slide, or if you have the computer within easy reach while you are presenting, you can press the 'B' key to send it to a black screen. Some fancy remotes even have a built in button for this purpose.
Don't neglect the power of not projecting anything.