The primary connotation of a Sketcher is an artist however with the prevalence of drug use in the artistic community the term became synonymous to drug abusers.
The Derogatory connotation a sketcher is a drug addict who is desperate for a fix, typical of a
methamphetamine addict but reflexively usable for any drug addict. The U.K. equivalent slang term is spranger.
Sketching can also be referred to as "Shrimping" where an addict is becoming so desperate for a fix they begin to shake violently and begin to search frantically for any substitute or for the substance of choice. The next step past Sketching is getting the Wheedles.
Calling someone a Sketcher can literally mean you are calling them a drug addict.
An
alternative connotation to a Sketcher is someone so angry they vibrate like a pissed off Chihuahua and could possibly cause anything flammable to
spontaneously combust.
Drug addiction connotations;
Example 1: Why you sketching so bad?
Example 2: Frank has been sketching badly. I think he is back
on the shit again.
Anger connotation;
Example 3: Lisa caught her boyfriend cheating on her again and she was really sketched out badly this time.
Example 4: I know why Dave has been acting like a Sketcher lately. He found out he was turned down for a promotion for the third time.