Create Glitter / Sparkle Overlay

It may be a completely stupid question, but is it possible to create semi transparent layer that can be applied to a background (color) to make it look like the attached image? If so, the job is to create the overlay in a 300 dpi quality and a size of 2500x2500 pixels.I guess you would have to out ins some white spots, and some (more or less) transparent black regions to make it work? I would like to be able to design such glitter images with different colors then by changing just the BG color.....