Looking at the apps in iTunes. I ran across
an app called Art Set. It has some interesting features.
You can select the color and style of paper you want
to draw or paint on.
When you select the paint brush tool icon, it opens
up a tray of different medium that you can chose from.
Oil paint / color pencil / crayon / oil pastel /
ball point pen / large marker / small marker
and of course for you people who make mistakes