relic

memento, remembrance, reminder

artifact

afterimage, aftertaste

balance, corpse, hangover, leftover, oddment, remainder, remnant, scrap

dreg(s), leavings, remain(s), residual, residue, rest

artifact, fossil

dinosaur

antiquities, ruins

hangover, remains, remnant, trace, vestige

dodo, fogy (also fogey), fossil, old-timer

fuddy-duddy, mossback, stick-in-the-mud, stodge [British], troglodyte

throwback

mummy

carnage, carrion

ashes

deceased, decedent