Adding themes

I can't add new themes.

i.e. I wanted to add stars. I added images star1.png, star2.png and star3.png C/P existing classes in .css snow1, 2 and 3 and change names to .MMM-Snow .star1 {background-image: url('images/star1.png');} made new theme "zvijezde" with "flakePrefix" : "star"

And module isn't working.

If I simply replace images, i.e. replace snow1.png with star image named snow1.png, it is working normaly with star images.

Same issue ...