This is my current length, but since I also have no photos of my first one of the first few months of having it, this will make due. This is about a month and a half later of getting the first hair cut. You can simply let the layers grow at this point. For styling, use gel, spray, and add some accessories too like cute headbands and clips to add some spice!
Now this photo right here is in fact me growing out my first pixie, and I decided to dye it brown at the time instead of my normal red. I would say at least 2 months later, perhaps two and a half. I'm still just letting all the layers grow, including my bangs. At this point and time, the hair on the back of your head along the nape of your neck is going to really start growing and your going to need to razor the short hairs closest to the skin, and getting trims on the longer upper layers. If you do not, your going to end up with an awkward and ugly looking mullet. You can also start doing more with your hair at this point, like twisting your bangs back or to the side. The headbands and clips will look even better in your growing hair.
Found this on the internet, the perfect example of getting a mullet by not trimming the nape of your neck while growing out your pixie cut.
I'm sorry but I could not find anymore in between pictures of myself between that last one and this one. This was months and months later, from fall to spring. Obviously, I have keeping up on trims since I do not have a mullet like the previous picture. I have let my bangs grow to the side, and now have even more options to work with my hair. I can braid my bangs back, or french braid them and the rest of the side to create a tiny pony in my hair. Or just a tiny pony at this point in general. However, your going to need to do something to keep the rest of your layers up if you choose not to braid. As always, there is always the options of headbands and clips. Only now you can combine them with more twists and braids.
Once again, from my lack of photos because I hate almost 99 percent of photos taken of me, so I rarely take them, here is a photo from months and months later. Almost the year and a half later. At this point and time, you can pretty much go crazy with your hair and do all sorts of things. For example:
The water fall braid
Hard to see, but it's braided down the back
Ever popular side braid
And although I do not have pictures of it, I was most fond of fishtailing my hair and also doing the french twist. Pretty much, when your hair is long, you have endless possibilites of all the different styles you could do to your hair, so I'm not going to even try and make a list.
Depending on how fast your hair grows, and the supplements you may or may not be taking, it could take much longer, up to two years or longer to get it to the point I was at. Or the same time. But really, to grow out that pixie cut, you NEED PAITENCE. And you must remember to trim the mullet please!
Good luck. :)