You could make ears from felt and sew them to the hood. You could also make elefant feet-esque shoe covers out of felt. Not that you'd have to use felt, but it's cheap and would look good. Maybe you could carve some tusks out of styrofoam, but I'm not sure how that would look. It you're extra-DIY, use some painted tree branches. Maybe string together some empty toilet paper rolls and cover them with material for the trunk. Definately paint your face! If you're skinny, you could wear extra large clothes and stuff them, since elephants aren't skinny. I'll leave the tail up to you.