I suggest that you do not get any tattoo until you are mature enough to know what you want permenantly etched onto your skin.
Do not get any regi tattoos until you have served in that regt. Otherwise you will look like the biggest cunt in whatever regt you do actually serve in or a complete and utter Walt cunt if you get to serve.
Your sister should not get a regi tattoo until she has been shagged by at least half of the regt.
Please post a picture of your sister showing as much skin as possible so that we can give suggestions as to what might look good on her. (I have deliberatly left that open for comments such as a pair of rotweilers, two gallons of spunk or the greadier guards.)