It's amazing how many characters I saw here, thought were hot, and then liked once I actually watched the show. First Zero No Tsukaima, then Rozen Maiden, Haruhi, and now Busou Renkin.
... still anybody know the artist, or if there's a set of these?
Urushihara Satoshi (it's in the tags in red) does a lot of what amounts to explicit fan pictures of other series, in addition to his own usual works. If it isn't one of his own series though, he usually will only do a few drawings of an particular character.