I mostly agree with Mastermind here... Esspeically in regards to Romans 14. The concept here is that the Holy Spirit will convict us of wrong actions, in those lesser things in life. I would consider tatoos less of an issue as swearing... For there is considerable scriptural support that swearing is wrong:
The tongue also is a fire, a world of evil among the parts of the body. It corrupts the whole person, sets the whole course of his life on fire, and is itself set on fire by hell.
All kinds of animals, birds, reptiles and creatures of the sea are being tamed and have been tamed by man, but no man can tame the tongue. It is a restless evil, full of deadly poison.
With the tongue we praise our Lord and Father, and with it we curse men, who have been made in God's likeness. Out of the same mouth come praise and cursing. My brothers, this should not be. Can both fresh water and salt water flow from the same spring? My brothers, can a fig tree bear olives, or a grapevine bear figs? Neither can a salt spring produce fresh water.
If anyone considers himself religious and yet does not keep a tight rein on his tongue, he deceives himself and his religion is worthless.
Now, having said that, I temper that with the fact that most profanity is culturally influenced. Certain words are profanity in one culture but just normal words in another. To that end, the meaning behind a swear is important, as is the conviction of the Holy Spirit.
For what it's worth, I still struggle with controlling my swearing too. It seems among some company it's no problem but among others it can be. But in the end we should all endevour to swear as rarely as is possible - and we do this through the strengthening of our will by the Holy Spirit, because our ability to resist sin comes monstly from God working through us, rather than by any strength of our own. Though, (much like those lustfull thoughts that sneek in) there are some for whom it will be a lifelong process. Take heart though, for we are sinners yet we are saved by God's amazing grace.