We have no idea what those six characters across the top of her back mean.
The same person also posted many of her photos in BMEzine.com, like this one:
http://www.bmeink.com/A40403/high/iam00022266.jpg
What does 喜 and 壽 have to do with Madsteel?
The most interesting ones are on her feet:
http://www.bmeink.com/A90318/high/f4dt-madsteels-footie.jpg
I don't think 鉄狂 has any significance in Chinese. (If she had 鉄拳 from the video game Tekken tattooed on her hands, that would be awesome.)
Alan's guess is that it could be "railway fan" or "railway maniac" in Japanese. Railway workers call them "foamers" (those guys that know the names and car types of every single piece of railcar traveling over the rails and Details magazine recently had an article about these railway fans.)
Remember the movie Trainspotting? In Japanese, railway is 鉄道 and 狂い is a common suffix for a maniacal fan of something, so 鉄道狂い could be shortened to 鉄狂.
Judging from the name of the poster, we guess her feet tattoo are supposed to be a sort of
translation of "Madsteel" but if so, shouldn't it be in the order 狂鉄? Notice this young lady has the same two characters tattooed on both feet, but in opposite order.
Also, 鉄 is only iron and steel should be 鋼.
Interestingly enough, there is a Japanese punk song by バミューダ バガボンド (Bermuda Vagabond) with the same title.