I have not seen a fatwa which explicitly prohibits tattooing. However, one has to be careful what picture or image will be tatooed. Anything which is immoral or with sexual connotations will, of course be haram. Similarly, it has to be remembered that praying with clothes which have images on them is makruh. One could possibly extend this ruling to cover tattoos also. My personal advice would be not to undertake this practice which has no Islamic basis. May Allah (SWT) guide us all.