C'mon people, it's so obvious!
The fact that the contents are glowing can only mean one thing: inside the chest is Marcellus' soul. Using the wayback machine, Tarantino visited the past and implanted a suggestion in Trampier's brain to draw this illustration, as a teaser / promo for Pulp Fiction.
The dude in the back is Marcellus, and is wearing a full-head bandage. As everyone knows, in the Bible it states that the Devil takes your soul out the back of your neck. The Devil knows this, and took Marcellus' soul, but all that was available to him was a rusty battleaxe and so he botched the job, leaving Marcellus with a nasty head-wound.
The illustration is also performing double-duty as a teaser for Reservoir Dogs. Now that Jules and Vincent have recovered Marcellus' soul, Marcellus is going to torch the two henchmen.
Damn that Tarantino is clever!