Aleš Lombergar

The easiest solution would be to cover the glass with an adhesive vinyl film ( similar to “Mac Tac” ). You can find this in stores such as Home Depot or Rona. It comes in a roll, in plain opaque, patterned opaque, frosted, solid patterns, translucent, clear, stained glass look, etc. This type of film is often used on bathroom windows, or door windows and sidelights. It allows light in while reducing visability into the space. You have to check the roll widths though, as you really don’t want to have seams on the glass.
For a more creative solution, you should look into coloured spray paints for glass, also available at the above stores. These come in many colours in a transparent , or a frosted finish. These again, will allow in light and reduce visability through the window. With these you can spray on one color, or create patterns and stained glass effects of your own by taping off areas and using a combination of colours in your design. It is easily removed with the proper solvents ( read the label ), so you can correct any mistakes or change your design if you tire of it.
So good luck, and I hope this helped.