Depends, are we talking specifically Christian here ? I think Christian images are fair game because theres so much of it and a lot of it is very nice to look at indeed (tho kinda bored seeing st michael do his thing) . I would be very careful with other faiths tho just in case you did cause offence , especially when travelling . I dont know whats blasphemouse or not with other faiths. Religious images , satanic images and mythilogical images are all cool things to get tattooed imo but I would not want to offend anyone (except maybe the mormons or Jehovas that come to my heathen door and hassle me !)