Looking through Nienhaus' sprite thread for clues as to what fits inside the engi cart, I can identify the fire extinguisher, extended emergency oxygen tank, multitool, crowbar, welding tool and wrench.
The Engineering cart can hold one of each toolbox, metal, glass, platsteel, flashlight and engineering tape. This is barely useful, and not to mention the engicart looks seriously bare.
Is it possible to add in further functionality? The ability to store a welding mask/goggles, gas mask, oxygen tanks, rods, station bounced radio, fire extinguisher, t-ray scanner, airlock/power/electronics boards, console screens, machine parts, mesons, folders/paper, etc would be very useful and ensure that it gets used far more often.
edit: also whiskey. It should be able to hold whiskey.
edit x2: but seriously, it should really hold AT LEAST the extinguisher
edit x3: also what are those little green things on the sprite sheets? Circuit boards? Is that grey tube thing a bunch of rods? Pipes?