Actually, I took a photo off of the front porch to use as a reference.
This way, the wind, dust, animals, constantly changing light source, and construction equipment would not interfere.
( also, I find it easier to try drawing from a 2d reference.)
I'm afraid I cannot share the reference however, due to privacy concerns.

Both of these were drawn with no reference.
The first I think looks like a caveman.

The 2nd is a phanto enemy from TTD.

Yup, another Pepsi can.
Did this one in crayon.

As an experiment, I limited myself to only 3 crayons.

I chose Cyan, Magenta, and yellow.

Same picture, but with a lot of touch-ups.
Found out that sticking it in the microwave will set the wax harder, allowing me to draw over, making touch-ups easier.

Otherwise, same 3 crayons.

That's really neat! The new version is a lot clearer-looking.

However, this makes me wonder if Crayola really needs to be selling crayons in 120+ colors!

You do make a pretty good point actually.
Out of a 96 crayon box, I used 3.

The following are some artwork that I had scanned at 1200 DPI as a functionality test for a 3-in-one printer that I had acquired, and were stored as .PNG.
As a result, they are absolutely massive. The file size ranging from 35 MB to 130 MB. (This is also too large to upload to imgur.)
With that said, here they are, future scans will not be this large except in special situations.
Re-host at your own risk.

http://www.mediafire.com/view/rn4cvvfam5sae1a/aphrodite.png
http://www.mediafire.com/download/xwjj66g9q51325p/coffee.png
http://www.mediafire.com/download/3uo3ekevpx9pvf4/eagle.png
http://www.mediafire.com/download/82rkrhyau5n2lbn/Horse.png

And of course, if you don't want to download the over sized versions (And I don't blame you).
Here are the smaller variants.

Pepsi cans

3-crayon version


graphite + charcoal version.
(sorry, the paper was crumpled)

That horse is awesome. I like the general vibe of Aphrodite the dog, but it would be nice if there was greater contrast between the dog's body and the ground.

And yes, you must have one powerful scanner to produce image sizes that large. That'll come in handy if you ever need to print one of your drawings on paper the size of a skyscraper!