I recommend using zerochan, pinterest and deviantart all in combination. The artist for this piece is KR0NPR1NZ over at deviantart. Try using the phrase "semi realism". You'll find that it nets you amazing results. Semi realism is basically my bread and butter for looking for art. Attach other key words to semi realism, such as "red hair" "blue hair" "black hair" "freckles" and "male" or "female". Typically you'll find more drawings/paintings of females. If using pinterest, make sure to specify "fantasy", "witch", etc. 

Sakimichan over at deviantart is also another amazing artist to peruse. Other amazing artists include: Sawitry, Jon-Lock, Lelenia, Kate-FoX.

So far though, [url=http://kr0npr1nz.deviantart.com/]KR0NPR1NZ[/url] is just the most amazing ever. Their art is just... phenomenal.