Testimonials Slider Using SASS and BEM

I couldn't find a good way to set the BG image in the CSS with Javascript, so I had to set the BG image inline in the photo div and use JS to change that. My JS slider solution is kind of crude, so I'd like feedback if anyone knows a better way to do it. I over-styled this one a lot to make it responsive and it's still not perfect...I'd be interested to see if anyone has a more elegant solution.