Original tiff image in an CSS-sprite

Hi!
I have an school task where an original picture is in a tiff format. The task is to compress the image to png24 and jpg in different bpp. Totally 7 pictures and they should be presented in a css-sprite. The original tiff picture is supposed to be in the background and the others to be shown when hover. The problem is that the tiff image won’t show. Yes I know tiff is for print purpose ?? But the purpose of the task is to show the different qualities when using compression. Hope someone can give a tip how to go around the problem. Can’t find an answer in the FAQ, only suggestions to convert to jgp.
The theme I use is a child theme of Twenty Fifteen.