if th ehole is in the top to let the smell out, and the eggs themselves aren't in contact with the material i can't see it doing any harm,
but will start to smell in about a week maybe 2. especially if i puts the heat on in the foot wells.
did a similar thing to a friends car, stuffed confetti in all the air vents, a potatoe up the exhaust, and gravel in the hub caps(note to others the gravel and drum brake sis a bad combination hers failed when she drove away, nothing serious happened, but she wasn't best pleased.) and we put fish on the engine in tin foil, just under the air intakes.