Hi kweb,
Thanks for reaching out to us.
We checked the slideshow on your site, and we can see that the gallery is currently using 1920×1440 (4:3) images.
You do not necessarily need to crop all of your property images to 1920×600. Property images can have different orientations/aspect ratios, and SP Property uses the gallery images for the property slideshow and generates the appropriate thumbnails for the listing views.
The main issue here is the display area of the property-detail carousel on larger screens. If you use a very wide ratio such as 1920×600, it will naturally fit the wide desktop slideshow better, but this would require cropping your original property photos, which is not ideal for a real-estate website.
We would recommend keeping good-quality original images rather than preparing every image specifically at 1920×600. If the slideshow height on desktop is too large with your 4:3 images, the better solution would be to adjust the carousel's displayed image height/CSS so that the original images are constrained appropriately.
There is also a previous SP Property case where the desktop carousel became excessively large with property images of different orientations, and a CSS adjustment was used to limit the image height.
If you would like, please provide a screenshot of how you would like the slideshow to look on desktop and mobile. We can then check the appropriate CSS adjustment for your layout.
Best regards,