We think in pictures so give them pictures:
Our brains work with pictures. If I ask you to think of a house, you see a picture of a house. You do not see the word ‘HOUSE’. So when the brain is presented with a visual stimulus such as a PowerPoint slide it can only do one of two things: Either it sees a picture which is easily translated and the brain relaxes, or it sees words/numbers which need to be deciphered into pictures which requires the brain to work.
So if you constantly show slides with lots of words and numbers you can expect to kill off your audience pretty quickly, perhaps within 5-6 slides. On the other hand if you are showing lots of pictures then your will relax and stay with you throughout the presentation.
Tips: Make sure the pictures are high quality, that they are pertinent to your talk and not simply some abstract picture and that they are large enough for everyone to see.