Like she said "shading" is a great step to move on to because it can be used from traditional hand drawn to digital art.
I may not be correct but it looks as if it was colored with markers. Not a big deal really, but some people don't like the
look of marker coloring since you get streaks and stuff. Try colored pencils. They're great for shading practice, transfer
pretty well when scanned (depending on scanner) and look nice.
Or if you want to jump into CG coloring. Draw your picture, but don't color; just redo the lines with a black pen or fine-point maker
and scan it. After that you can use a program to color it. A free one is know as paint.net. It's not as good as photoshop or those
other $100 programs, but for freeware it's the best out.