I once saw a background something like this in a craft magazine and have been "going to get around to" trying it ever since. The "Make your own background" challenge at Craft Room Challenge finally gave me the impetus I needed.
I started with a piece of white card the same size as my base card (so that I could later trim it to size, removing any edges that had got messy where I'd been holding the card) and stamped small swirls and clusters of snowflakes all over using clear ink embossed with clear embossing powder. If you wanted a more strongly defined look, you could use white instead of clear.
I then sponged all over in various shades of blue dye inks, ranging from a slightly purply one to a turquoisey one, and keeping the darker shades mostly towards the outside. I buffed the whole surface hard with a tissue to remove any stray ink from the embossing, then gave it a blast with the heat gun to make sure it was completely dry.
Next I stamped all over in white ink with a stamp of tiny random dots. You could use a Versamark pen to give a similar effect. I sprinkled this with hologram embossing powder. Then I stamped the larger snowflakes in silver ink and sprinkled them with silver embossing powder. I didn't heat-set the hologram powder before I did this, partly because hologram powder burns easily and wouldn't like to be heated a second time, and partly because I wanted a tin y bit of the silver to be picked up by any dots that hadn't been fully saturated with hologram powder, just to give it a little extra sparkle. So both lots of stamping were heated at the same time.
After trimming the edges, all the card needed to finish it off was a little ribbon and a die cut snowflake.
I've photographed it in several different light conditions as each seemed to emphasise a different aspect of the background.