Support local street art by reaching out to DC's graffiti/street art organizations. Encourage talented youth and street art veterans, who may otherwise illegally turn their cans to private and public property, to work together to create scenes and statements that reflect each station's character. The larger transfer points, like L'enfant, Gallery Place, and Metro Center could pilot this migration from the streets to the subways.
The $100,000 would cover the materials and supplies. Work with the organizations to keep labor costs minimal. For instance, a student or veteran could earn the privilege of designing a wall at Gallery Place with the support of their community art organizations and the oversight of Metro management. Beyond the immense walls, the geometric pattern in the curved ceiling offers a lot of additional creative space for artists. Such a project would draw tourists who want to witness new cultural landmarks unfold, while also generating local pride for DC's vivid initiative to reflect on itself as the city changes. The featured picture is of a DC mural in Bloomingdale from http://happy-accidents.tumblr.com/. The six month time frame would be enough time to pilot at least one mural from a community-based "work-trade" with local artist groups.