On his blog, J.D. mentioned that his monsters are on the Swords & Wizardry SRD site. Since there is nothing cooler than seeing your monsters illustrated, here is J.D.'s gump, along with the illustration from Monstrosities.
Hit Dice: 4
Armor Class: 5 
Attacks: 1 weapon (1d6+2)
Saving Throw: 13
Special: Gaze attack paralyzes (+2 save)
Number Encountered: 1d4
Challenge Level/XP: 5/240
Gumps are large and blubbery humanoids with an overly broad jagged toothed grin and a pair of small, deep-set eyes in an otherwise featureless face. Gumps are motivated by hunger and the deep down joy they feel when murdering a helpless foe. Anyone meeting the gaze of a gump must save vs. paralysis at +2 or be held in place for 2-5 rounds (fighting without looking incurs a -4 penalty to-hit). It is safe to view a gump’s reflection in a mirror or other reflective surface. The gump is able to squint in an odd manner which keeps it from paralyzing an ally.
— Author: JD Jarvis
Gump: HD 4; AC 5; Atk 1 weapon (1d6+2); Move 9; Save 13; AL C; CL/XP 5/240; Special: Gaze attack paralyzes (+2 save).
I think the artist is Stan Morrison
(Edited to link Monstrosities and Stan Morrison)