Wordpress slider that can handle transparent pngs?

I’ve just found out, annoyingly that the Nivo slider cannot handle transparent pngs as slides.

If I remove the background of the slider, it just stacks them on top of each other against the page background as they rotate in.

Does anyone know of a slider I can use where the slides can show one by one over the page background without this stacking effect?

Hope that makes sense!

Thanks,

Jon.