While I love the idea of making the results slides more meaningful, I'm not a big fan of using thumbs up and down imagery. I have a few reasons for feeling this way.
First, thumbs down imagery has negative connotations (it is used to express dislike on blogs and sites like YouTube) so I am wondering if by using it in our courses we are inadvertently passing judgment on the learners.
Second, hand gestures have different meanings in different cultures. The thumbs up gesture is considered offensive in some parts of the world. I won't go into what it means here but you can look it up if you are interested.
Finally, strictly from a design perspective I think these gestures are over used and there must be more interesting ways to denote correct and incorrect responses.
I'd be interested in hearing if anyone else has any thoughts on using thumbs up/down images in courses.