Pocket squares!! Love them.
Wouldn't do it for an interview though. Too ostentatious.
A white one in a TV fold, perhaps, but otherwise no. Especially if you aren't used to wearing them. I wear one at work almost every time I wear a jacket or jacket/tie (wearing one now with just a jacket). You have to get used to it because people notice and call you out for it. It's honestly not something I'd experiment with on interview day.
For interview ties, you want to go with a traditional color (burgundy, navy, etc) in a traditional scheme (repp/stripe, solid, grenadine, etc.). Most ties are fine, but if you are buying something, it makes the most sense to buy something with a bit of textural interest because it ties the outfit together (PUN!). Visual interest is best done with things that don't jump out at you, i.e. a light herringbone, a grenadine/weave/knit. Like I said before, shiny things are bad. They look cheap. Applies to suits/ties/etc.
The tiebar site seems to have a lot of ties at a reasonable price. Ebay has a lot of good stuff if you know what to look for (Brooks brothers ties go for 10-15 bucks used).
While I love wearing them, I steer clear of paisleys and bold patterns for interview ties. As I've said before, the point of dressing for interviews is to look well put together without having anything that jumps out at someone. You want your experience and words to do the talking, not your clothes. I am confident that if you spend the time to get a well fitting suit and have it altered by a competent tailor, then you will already be in the best quarter of men interviewing. Provided you make a reasonable tie and shoe choice.
It really isn't that complicated, but if you see something and are like WOW THAT LOOKS INTERESTING, it's probably not the right tie or shoe or even suit for the job.
I love windowpane suits, gun club check, Prince of wales overchecks etc etc. I have sportcoats with all those things and will probably buy a suit with them when I need to have more of a suit rotation, which will probably only need to happen by fellowship. They look great, but are attention getting, which is the opposite of what you want. I like nice clothes and suits and ties, etc etc etc. but interview attires is an entirely different ball game.