sketchmonger 

One who brings about sketchiness to most, if not all, situations; one who harbors sketchiness

It wasn't surprising that Nina didn't answer her calls or texts, because she was a well-known sketchmonger.

sketchmonger by Erin "Patches" Murray July 31, 2011

sketchmonster 

One who is sketchy in monstrous proportions.

One who is very, very suspicious or acts in suspicious ways.

(Random guy hides behind a wall.)
Person 1: Dude, look at that sketchmonster behind that wall.
Person 2: Yeah, seriously. Look at him. Standing behind that wall.

sketchmonster by Pdoany. February 25, 2009