Let’s start by explaining what a spacesuit exactly is. They can be classified roughly as three types:
Transport suit (which is not a de-facto spacesuit, just a pressure suit) - this is the one (most probably, discussed further down) being created by SpaceX.
EVA suit - this is the most popular type, known from many pictures and memes.
Martian suit - this is the one we haven't got yet.
What SpaceX is working on is a spacesuit to travel aboard the Dragon - we don't have a complete idea of what its functions are, but most probably it will be something similar to the famous "oranges".
This is how the famous orange suits worn by shuttle crew look like.
SpaceX is creating a counterpart of this one (as well as a few other types, probably with a similar design);
Over a year ago, on a closed forum for space specialists - NSF L2 - this picture was posted. It wasn't, however, spread to the public and was agreed upon to be fake.
Most probably we can see a prototype from around the start of 2015, maybe even the second half of 2014.
What's interesting is that it looks similar to what we see on the video from September 2015: (what's more interesting is that it is supposedly not CGI, but real actors dressed in prototype suits).
It evidently looks like an earlier prototype of what Elon Musk showed off by the end of September in... fashion magazine Vogue.
We can see better material, a different color, but the idea is the same. A panel beneath the neck has the same chrome finish, as does the helmet screen, we can see similar pauldrons and the same logos on the arms.
It's no secret Musk wants the suits to be as pretty as possible - the ordinary Joe is supposed to imagine wearing it and flying it to Mars.
"If we want to inspire our next generations to go beyond Earth, they need to want to wear these suits. It's very easy to make a suit like that to be thick with many elements standing out”.
We also know that the man responsible for the SpaceX suit is Jose Fernandez, who makes suits for superhero movies. He was the man responsible for designing, among others, the suits in Batman vs. Superman, Iron Man or The Avengers. In an interview which has escaped the public eye a bit he said: "SpaceX, the company helmed by Elon Musk, got in contant with me to ask whether I would like to make a spacesuit. I had no idea it was for SpaceX and I thought they meant some movie. Only later I understood that it's for the space program. They were looking around for someone to build them a suit like that. They've had two weeks to present a prototype to Musk and when the time came to show it off, they didn't like anything but my helmet. I've worked with Musk for half a year and we've been able to create a suit which they are now reverse-engineering to make it a functional model. It looks like it will be previewed in the upcoming months (the interview was in February). Elon wanted it to be stylish. It has to be practical, but it also has to be awe-inspiring. This is seriously pretty badass. He kept repeating - "everyone looks better in a tuxedo, no matter how big he is or what is his body shape" - and when people wear their suit, it is supposed to be like a tuxedo. They are supposed to look in it better than without it. You're supposed to look heroic. It needs to be an icon".
SpaceX worked with Orbital Outfitters before (http://orbitaloutfitters.com/), but it seems they didn't make badass enough suits. Nowadays, most probably, they do everything in-house.
- the cutting edge of technology is being used (like they usually do), among other things, from diving suits;
- it will have some emergency systems to abort EVA;
- is an initial line to a whole family of spacesuits (pressure, EVA, Mars).