TMBTM's idea doesn't sound bad.

The skeletons start spinning, beams shoot from them into Spalko, she starts receiving images and then she melts, explodes, or bleeds from her orifices.

I'm thinking, instead of newsreel footage, how about lots of random disturbing images of death, decay, disease, distruction, etc. They could be overlayed (transparent) Spalko standing there, or quick, rapid, epileptic siezure inducing intercuts.

While I agree that they should have gone for an artifact or something more embedded into the collective unconscious (a REAL City of Gold, the original Cross, the Fate of Atlantis, the Infernal Machine, proof aliens built the pyrmaids, the last lightsaber (it did happen a LONG time ago)...), the mythology of 13 crystal skulls was not invented for Indy. It's just more obscure.