Hi Aspirant!

There is no such restriction on candidates regarting tattoos in civil services exam. You are eligible to write the exam like any other candidate.  As long as the tattoos are not vulgar, or they are of religious significance, you do not stand a chance to get disqualified on the basis of a tattoo. But during interview, you might face questions related to your tattoo, specially if it is clearly visible.

Thankyou!