What is the drawing on Tomoko's shirt? In episode 4, Tomoko is using a shirt with a drawing.  

  

The shirt has a drawing of a face, and すぐる (suguru) written on it.

Since this series makes references to others quite often, I wondered if the shirt is a reference to something.
If not, does the shirt have any significance at all?
http://www.wordsense.eu/Suguru/ seems to define suguru as "male given name".
As far as referencing goes, I think it'd be reasonable to say it's just a picture of a guy's face where an equivalent to "guy" is written underneath.