As I mentioned in an earlier entry, Carnaval is not limited to the larger urban centers. The blog Almada de Noche spent some time with his friends in the little town of Arbieto, 30 km from Cochabamba. The small town is helped supported by remesas (remittances) sent from abroad. The festivities obviously lack the blatant commercialization of their counterparts in Oruro and Santa Cruz.
There are some great pictures, including Carnaval masks depicting the Incredible Hulk and OBL. See his entry here.