Suggestions for pocket square with this tie.

Honestly, I either change the shirt to sky blue or change the tie to forest green aka dark green.

then move on to the pocket square.

This looks very fashion-forward to me.  It's hard to give a view without knowing what sort of look you're aiming for, and what other people will be wearing at the wedding. 

But for my part I would never wear dark shirt and a light tie (indeed, I'd never wear a dark shirt with tailored clothing full stop).
 

What sort of suit will you be wearing?

"My wedding" as in you are the groom? There are strong feelings against wearing dark shirts here (which I share), but this would be an even more egregious mistake if you are the groom.

I too vote against a dark shirt. I own one in a similar shade to the one you have and I have never found an appropriate way to wear it. If you want to wear that tie then I say go for a white square.

+1 against a dark shirt. If it's for a wedding then go formal with a blue or white shirt, add some play with the tie but keep it serious.
 

Good god man, definitely ditch the shirt...

 

Now that I'm seeing it I don't even know if a light shirt can save that tie.

^ I've got to echo this.  I don't want to be snarky given your big day is coming up, but you asked for advice:  I would change the shirt to a pale blue (if you want to avoid the formality of white) and find a different tie. 

 

If I was aiming for informality myself, I would achieve it through choosing a suit with some texture and in my tie choice.  (Not that I would shoot for informality at a wedding.)
 

I'm sorry, but yes it is. Showing your personality is one thing but this is a mess. If I might make a suggestion, take a look at the WAYWN threads. There are some excellent shirt/tie/jacket combinations in there. Some of them are rather unexpected combinations that work. Which is a wonderful way to express your personality while preserving good taste.

I should have commented when I saw this post pop up yesterday, but it sounds like everyone shares my exact thoughts anyways.  

 

I'm generally not a fan of darker shirts, and my dislike of them is even more pronounced when they're worn with a suit - it's like a muddled abyss of dark color on somebody's front.

 

Remember, the whole idea behind pairing suits, shirts, ties, and pocket squares is to guide the viewers eye to your face.  With the combination you currently have our eye is drawn first to this bright, light blurry thing running down your chest and THEN to your face (that is, if we can peel our eyes off that tie :))

 

But there is good news.  You have two good things going for you.  First is your own contrast - you have light skin and dark hair, giving you a high contrast.  This opens up TONS of suit/tie/shirt/pocket square combos for you.  Low contrast guys like myself I feel have a lot less to work with.  Second, you already have a nice charcoal grey suit - a perfect foundation.  

 

As was mentioned in the previous replies, ditch the shirt and the tie.  Go for a lighter colored shirt - white or light blue - and a dark tie.  This will match your own high contrast, so there won't be any particular color that stands out (like your current combination).  As to your original question about pocket squares, I think it will depend on your shirt/tie combo.  But when in doubt, white always works.  There are also many different ways to fold them - just don't get too swanky (ie. a triple point fold or something crazy like that).

 

If you're on a tight budget, you can get ties and pocket squares on the cheap at http://www.thetiebar.com

^ Agreed, although I'm not crazy about the tie. It seems a bit silly for a wedding, especially since you're the groom to be.

I'd go classic white shirt, bold tie. Not "business" like but definitely serious.

You can play with the color and texture of the pocket square though. I love the 3rd one.

I stay firm of my initial suggestion.