There's no difference between 'edited artwork' and 'classical sprites'. The artwork you've created on paper is reduced in size to resemble the sprite you want to make. That art will simply serve as your guideline for the placement of pixels; it's a base. If you had no artwork at the base and just worked from the blank canvas, it's just a matter of using your mind's image of the same thing as the guideline for pixel placement.
The comparison between the two images here gives you an example:
http://www.derekyu.com/?page_id=222http://www.derekyu.com/?page_id=223There are a multitude of ways to create the same thing. Reaching your goal is independant of the method you used to reach it. In this case, you can go with at least these ways:
-Take drawing, scan and size reduce. Use the drawing as a guideline to create the outline, then eliminate the original drawing. One is left with a simple outline that can be colored and shaded.
-Take drawing, scan and size reduce. Turn the drawing into a silhouette and eliminate any leftovers from the original drawing that are unneedd in your sprite. This silhouette can be manipulated into your sprite.
-Look at your drawing and try to mimick it's outline/silhouette on the blank canvas. This outline/silhouette is then used to make your sprite.
-Don't make a drawing and put onto the blank canvas an outline/silhouette of your mind's image. This outline/silhouette is then used to make your sprite.
-Just put pixels on the canvas of a rough concept and see where that leads to.
All of that is identical for every single sprite you're ever going to make. You don't need to 'learn' how to make enemy sprites, you can make every sprite the exact same way. If you can make one, you can make another. The only limiting factor is your own creativity, skill, knowledge and perseverence.
Remember that spriting allows unfinished possibilities of tinkering with what you have. You can endlessly tweak an image to perfection as you make back ups of your work in progress and experiment with different means of changing it. If you don't like how something looks? Just move about a few pixels and it would look totally different, aking to using the eraser to remove a line to draw another.