I've seen some prototypical attempts at converting stormtroopers and such, but I've just found a quick and easy solution:
Those are New Swabian League (GZG) Armored Infantry painted white, given the proper helmet details. I didn't do a very good job on them... I just sloppily painted on a few layers of white (so used to Foundation Paints now that painting more than a little bit of white or other non-foundation colors is an absolute pain), painted black in the gaps in the armor, painted the guns grey (makes them stand out a bit against the black and white), and painted on some of the helmet details (how detailed I went varied from model to model, a bit, and I pretty much just painted the 5 main dots in the right zip code and called it done). I'm sure a more skilled/less impatient painter could do better... probably even myself, but I want to get playing!