I decided to spice up the preliminaries a little and accept a few OC's! I'll give you the template at the end of the chapter. I'll be taking one extra team, so the three OC's I like most from those posted shall appear in the preliminary rounds. I can't promise they'll show up that much from then on, but at the very least I won't be a jerk and kill them all off.
So here's Chapter 12.

The second exam took place in a deep forest ominously entitled the "Forest of Death". The instructor, a young woman called Anko, informed
them that they would each be given a scroll with the symbol for either Earth or Heavens on it, and that they had to make it to the tower in
the centre of the forest within three days carrying both a Heavens and an Earth Scroll.
"But wait a minute", asked Sakura. "Doesn't that mean only half the teams can pass?"
'Well that's stating the obvious', thought Naruto.
"Yes, that's correct", said Anko. "But no-one expects nearly as many as that to make it".

"Can you tell me anything about the place where we are going?" said one of the two cloaked figures as they glided through the forest. "Or
at least why we are wearing these cloaks".
"The cloaks are to avoid drawing attention to us", said the other. "And as for where we are going..."

Soon, Naruto, Hinata and Sasuke were deep into the forest. They had managed to get this far without coming into conflict with any other
squads. This meant they were still all in good health, but also that they were still missing a Heavens scroll.
"Get down!" warned Sasuke as several kunai flew towards them, hitting the trees behind them with a thunk. Naruto looked up into the trees to see a Hidden Grass ninja wearing a thick purple rope as a belt.
"Alright! Another team!" said Naruto. "Psycho Cut!"
The tree branch the grass ninja had been standing on was cut from the tree, but the grass ninja vanished. The three Leaf Genin spun round to
see that the ninja was now behind them.
"Now, let's begin... With our lives at stake!" said the strange ninja.

"Oh no you don't!" shouted Naruto. "Psybeam!"
The rainbow-coloured beam hit the grass ninja in the face, knocking her to the ground...
...where she dissolved slowly into mud.
"A mud clone", said Sasuke.
A group of snakes sprang from nowhere, constricting around Sasuke, as the grass ninja appeared again, and sinking out of the ground.
"Let's make this interesting", she said, forming hand seals.
"Summoning Jutsu!"
A gigantic brown snake appeared in a puff of smoke before lunging at Naruto, who dodged to the side.
A Summoning Jutsu, an attempted genjutsu, Mud Clone jutsu and superb dodging reflexes? thought Naruto. This clearly isn't an ordinary
Genin.
Naruto read his opponent's mind, but what he found came as quite a shock.

For a start, this was no grass Genin. They had actually killed a grass ninja and were now wearing their skin. Their appearance in the Chuunin
exams was also questionable, since they were actually well above Jonin in skill level. In fact, as far as Naruto was able to read, their
power was...
...comparable to Mewtwo.
"Sasuke, Hinata, we have to get out of here", said Naruto, with a tone of urgency. "This guy isn't a Genin competing in the exams. He's
stronger than any of us, stronger than even Kakashi-sensei!"
Naruto used his Psybeam to blast the snakes off Sasuke and the three of them ran away from the bizarre snake-man, but the huge brown snake from before curved around in front of them and blocked their escape.
"Leaving so soon?" said the snake ninja, in an entirely different
voice which Naruto suspected was his true voice. But he didn't get a chance to do much else before the snake swallowed him whole.
"Naruto!" shouted Hinata.
"It's too late for him now", said the snake ninja.
"Psychic!" shouted a voice from inside the snake. The snake seemed to temporarily go insane, its tail smashing the surrounding trees, before
it finally opened its mouth and Naruto leapt out, just in time to stop a second snake from crushing Sasuke with its sheer weight by using his
Earthquake to knock it off balance then attacking it with Ice Beam.

A smaller snake wrapped around Naruto's waist and pulled him in front of the snake ninja.
"Yes, I've heard of you, Naruto Uzumaki, Jinjuuriki of the Nine-tailed Fox", he said. "In the future you'll be crucial to my plans, but right
now you're just in the way"
He raised a hand glowing with chakra, and thrust it into the seal on Naruto's stomach. "Five-Pronged Seal!"
Naruto screamed in pain before he was thrown aside, crashing into a tree and falling to the ground.
"Your turn, Sasuke".
Sasuke was paralysed with fear. There was nothing he could do to fight this guy...
"Foolish little brother..." said a red-eyed figure in Sasuke's memory.
'No!', thought Sasuke to himself. 'If I can't defeat this guy, I'll never be able to defeat... him'
"Sharingan!" shouted Sasuke, his eyes turning red with black marks.
They resembled Kakashi's Sharingan eye, except each had only two marks where Kakashi's eye had three.
"Yes", said the snake-man, as if he had just seen what he had been searching for the whole time. "Those eyes, they're just like Itachi's!".
"What do you know about Itachi?" demanded Sasuke.
The man laughed an ominous laugh.
His neck extended out and he bit Sasuke in the neck.
"What did you do to me?" asked Sasuke as a mark resembling three of the marks in a Sharingan eye appeared.
"A gift", said the man. "My name is Orochimaru. If you want power, seek me out".
And the man turned to leave the area as Sasuke lost consciousness and fell from the branch he had been standing on.

So that's chapter 12, or Chapter Arbok. And here's the template:
Name: Speaks for itself. No Uchihas, no Uzumakis, no Namikazes, and no Senjus
Age: Again, speaks for itself. Remember that this is the Chuunin exams. At this point, most will be around 12-13 at this point, but I
might bring them back post-timeskip
Appearance: Again, speaks for itself.
Personality: Describe their personality.
Elemental affinity: Fire, Water, Thunder, Wind or Earth. You can have a mix if you wish.
Jutsu: Favourite or unique jutsu. Don't overdo it.
Bloodlines: Again, don't overdo it. No Rinnegan users, for example
Other notes: Anything else you'd like to mention.

Three of them appear in chapter 14.
Next time, we'll see two battles in the forest of death before the Chuunin Exam preliminaries begin. And also who the two cloaked guys are and where they're going. See you then.