Carousel Best Practices
When adding images into the carousel widget, we recommend making all of the photos the same relative height and width.
For example, if the first carousel photo is 1200 pixels wide by 200 pixels tall, each of your other images should be the same aspect ratio (width/height ratio), e.g. 600 x 100, 900 x 150, 2400 x 400. This ensures all of the photos will show at the same size within the area they are kept in.
As a recommendation, we use an image size of 1600 pixels wide x 400 pixels tall when setting up new carousels.