Actually there's a much simpler solution.
Don't bother waiting a year, you'll probably just forget. If you really want to make sure you want a tattoo...

Design it yourself.

It's as simple as thinking for yourself! Come up with and draw (or loosely sketch if your skills aren't up to scratch; you can always describe it to the real artists who are going to be inking you) your own design, and you're putting that year's worth of effort and thought into it in concentrated form. You'll soon have decided if it's the deign for you.
Plus, let's face it, anyone who walks into a studio, points to a pic on the wall and goes 'derr I want dat wun' deserves all the regret they get.
(Falstaff's Spiritual Successor, Wed 26 May 2010, 13:15, 1 reply)

I (sort of) did this.
When I wanted to get my first tattoo done I was on holiday in Spain and had no access to a printer, so I brought my laptop into the tattoo parlour and just showed the guy the picture on the screen. He drew it out freehand in a couple of minutes and did a bloody amazing job.

Side note to this story: I was back in Valencia a couple of years later and wanted to get another piece done, but I'd lost the guy's business card, so I spent a whole evening wandering around the quarter looking for him. I didn't find him but did find another parlour, so went in on the offchance that the artist was working there now. When I showed the owner my tattoo to see if he'd recognise the artist he said "Oh no, that wasn't done here - it's much too good."
( .Yeti. El amor en los tiempos del cólera, Wed 26 May 2010, 14:36, closed)