After giving it more thought, I realized that you can create image revealing effects by using the transition and animation settings in Google Slides. Basically, you layer one image over another and then arrange the transitions and animations so that the top image disappears when you click on your slides. I recorded a short video about how to do that. The video is embedded below.
Video - How to Create an Image Revealing Effect in Google Slides
Applications for Education
As I mentioned in the video, using the image revealing effect could be a good way to create a series of quiz game slides. On each slide you can have a question for which the answer is hidden until you click on the slide to reveal the answer. That could be a fun way to host to an in-classroom review game that is kind of like Jeopardy.