Rum Sleg's costume was present in the crowd of the Boonta Eve Classic. It stands to reason this was Rum. Rum Sleg was named for his Young Jedi CCG card after Dan Bojanowski's Star Wars RPG character.
In the comic, "Survivors", an individual similar in appearance to Rum Sleg was killed by Uda-Khalid, and was visible among the crowd of Uda-Khalid's victims.
An action figure of Rum Sleg was made for Hasbro's 2009 Legacy Collection. The figure featured a removable helmet, which did not reveal Sleg's face behind his faceplate but does show that he has whitish, lumpy, slimy skin and a brace of dreadlock-like appendages that are tied back in a ponytail. Whatever species Sleg may be, it is therefore confirmed that he is not human.
↑Chuck Kallenbach (@chuckkallenbach) on Twitter: "Absolutely. I was running the RPG on my kitchen table in Virginia Beach, and everybody named their own characters, of course. Dan's was named "Rum Sleg," and his battle cry was "Just Chill"! Is that all you need? (In response to "Hi Chuck, could you confirm on here that Rum Sleg was named after Dan Bojanowski's Star Wars RPG character? We need something outside Wookieepedia to reference it to!")" (backup link)