Good morning rockrats!
First of all, I should warn you, there will undoubtedly be a few replies to this thread telling you anything from you haven't got a hope in hell, to chaps merely stating their distaste at your personal preferences. All are opinions, and all are equally valid.
That out the way, this is a very mixed argument - to cut straight to the chase, I am a first officer with a particular low cost Irish airline based out of Stansted, and half my back sports a very trendy looking Chinese dragon. Whether I regret that (which I don't) or whether it will look as 'trendy' when I'm stood in the shower aged 80 (which it probably won't) is not the issue here. Tattoos in themselves do not hinder you whatsoever in achieving a Class 1 medical, and so they shouldn't. The reason I mention this, is that some airlines perform their own medicals on you as their medical requirements are slightly more stringent or particular than the JAA Class 1. Whether the tattoo is on your back, the sole of your foot (ouch!) or your forehead, they may or may not accept you on this basis alone, I couldn't possibly comment. A prime example is British Airways who perform their own medicals on air crew.
However, my tattoo is obviously not visible when wearing a suit (as I did for my interview at East Midlands) or when in uniform, and it wasn't a problem because my airline don't conduct their own medical - so long as you hold the Class 1, that's not a problem.
Of course had I shown up to the interview and they saw the edge of a tattoo, for the sake of argument, on my wrist, they may have brought it up, or they may have said nothing and sent me the polite 'no thank you' letter a few days later, I honestly don't know.
As a summary, my opinion is this may prevent you from flying for CERTAIN airlines, but there are many (if not the majority) that don't have their own internal medicals (discounting random drugs testing), and so long as you are a professional individual, and when you turn up to that interview, or are at work, that tattoo is hidden from sight, I shouldn't think there would be a problem. Also remember that we mustn't consider only the itty gritty legal stipulations here, but professionalism, and I always wear a plain white T-shirt underneath my work shirt to make absolutely sure it is invisible to the eye.
The tattoo behind your ear, whatever sentimental value it may have for you, I would consider having that removed by laser surgery, as I have never seen nor know of an airline pilot with a tattoo anywhere on their neck or head.
Regarding the ones on your forearms - if I were in your position and made it to an airline, I would have all long sleeve shirts - that way, you can keep them down when you're interacting or within sight of passengers/airport staff etc, then simply roll them up if you wish on the flight deck. I have flown with a couple of captains in the past who have done this, no problem.
You seem like a decent chap, the best of luck to you
Ad.
p.s. in case you haven't heard, the economy's bad at the minute. Try to spread out your training over a couple of years or so at least if you can!