The Ripple transition is a combination of 2 effects. It's a Cross Fade Transition between the two pieces of media. And the Ripple effect is the second effect. If your working with media with a lot of white in it. As the ripple effect kicks in the image collapses and edges pull inward. That's the canvas default Background color. You could change it to any color you want using the color picker.
Unfortunately, the background will be the same throughout the entire project. So that trick only works for similar colored media. And it won't be perfect.
If the entire image is fading. Try Right clicking transition and Un-Checking Use Trimmed Media in Transition.