That's a very cute 2K-tan.
I think this is adorable, there was another version on Wakachan with a teal outfit, I think this picture was photoshopped green. I happen to like the green one better though.
German cosplayers as ME-tan and Firefoxko! I happened to find some info on them as well!
http://www.wakachan.org/os/res/5244.html They happen to visit the Wakachan board.
http://kirameki.snow-sugar.de/blog/2005/05/07/metan_and_firefoxko_cosplayer/ The Japanese hunt for OS-tan cosplay as well.
Another German. I don't know much about her because her website and cosplay site are in German. If anyone can translate that would be great.