I see no problem with a small Catholic tattoo other than it is altering God's creation. I don't know of any pronouncement of the Church, anyone have one? If the Church hasn't said anything maybe it's acceptable but not recommended. However, if the saints take makeup this seriously I really can't imagine what they would say of tattoos.
St. Cyprian, Bishop of Carthage, Father of the Church (De Habit. Virg.):
“I hold that not only virgins and widows, but also wives and all women without exception, should be admonished that nowise should they deface God’s work and fabric, the clay that He has fashioned, with the aid of yellow pigments, black powders or rouge, or by applying any dye that alters the natural features. . . They lay hands on God, when they strive to reform what He has formed. This is an assault on the Divine handiwork, a distortion of the truth. Thou shalt not be able to see God, having no longer the eyes that God made, but those the devil has unmade; with him shalt thou burn on whose account thou art bedecked.” (Quoted by St. Thomas Aquinas, Doctor of the Church, in the Summa Theologica, Second Part of the Second Part, Q. 169, Art. 2)
St. Anthony Mary Claret, Archbishop of Santiago and Missionary:
“Now, observe, my daughter, the contrast between the luxurious dress of many women, and the raiment and adornments of Jesus… Tell me: what relation do their fine shoes bear to the spikes in Jesus’ Feet? The rings on their hands to the nails which perforated His? The fashionable coiffure to the Crown of Thorns? The painted face to That [of Jesus] covered with bruises? Shoulders exposed by the low-cut gown to His, all striped with Blood? Ah, but there is a marked likeness between these worldly women and the Jєωs who, incited by the Devil, scourged Our Lord! At the hour of such a woman’s death, I think Jesus will be heard saying: ‘Cujus est imago haec... of whom is she the image?’ And the reply will be: ‘Demonii... of the Devil!’ Then He will say: ‘Let her who has followed the Devil’s fashions be handed over to him; and to God, those who have imitated the modesty of Jesus and Mary.’”