Diamond shape images Slider Revolution

Hi all! I try to create diamond shape images into the Slider Revolution like you can see ?here. Unfortunately I cannot figure out how to create diamond images in Slider Revolution.

Actions:

1. I created custom square shape in Slider Revolution.
2. I rotated the square shape 45 degrees. So far so good!
3. I changed background of square with layer CSS:
{background-image: url(“../wp-content/uploads/2016/04/SBLi-brand-signs-G-STAR-RAW.jpg”);}

Result:
1.. Background image viewed in slider-revolution customizer but not on front-end website.
2. Background image rotated together with the square, how do I rotate back the background or is there a smarter, easier way to create diamond images in Slider Revolution?

I should be great if someone has a solution! I attached a image for better understanding of my diamond image issue ??