there is option "Preview items when clicked in media manager" in advanced configuration. But it's the same option for songs and images. When I want to change background for lyrics and I click on image - it change preview. I think it would be better to have option "Preview item on click" for songs and other for images or option "change background preview on image click"
And one another request function is "random change background for each slide" - to change background on slide changing.