What all is possible to draw?
Very easy told everything... from classic common graphic creation (logos, flags, signs, silhouettes...), through animals, flowers, cars, planes, assorted things til to portrait for instance.

Classic common graphic creations - logos, signs, flags, silhouettes etc.
      More specimens:
More specimens
More specimens
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What is important for high quality of drawing picture?
For really high quality of vector picture is important to draw it in high extension (from 1500% up). When the picture is in so extension, we can to see on the monitor usually fragment only (for example quarter of eye). For realistic look the picture have to be formed on pattern (photo). If it is not drawing on the pattern, can be both eyes in other scale for example... So most important is not only artistry of drawer, but also quality of photo. Digital photo in size and resolution of 17” monitor (for example wallpaper) usually is enough. When the photo is fit, the vector picture is often indistinguishable from original at first sight (see comparison of picture of ocelot and pheasant)
original rastr: 2,5x zoom: 5x zoom: vector picture: