We report on a novel nanoparticle platform by electric field assisted assembly, which is capable of manipulating the refractive index distribution through controlling the particle assembly. Two examples based on the control of the scattering properties are presented. We demonstrate lensless imaging in such a system. In addition, we show that random lasing can be enhanced by assembly of anisotropic particles immersed in a gain medium. These examples illustrate that particle assembly technique provides a promising platform for reconfigurable optical applications.