Planning is in progress to add California vegetation land cover shapefiles. The state has some good land cover shapefiles on the Department of Forestry and Fire Protection site. They are sorted by county. The smallest are under a meg while the largest - Fresno - is more than 400 megs. The average size is around 30 to 40 megs. These would be a great addition to OSM since they contain valuable metadata. Once the areas have been added, the state will take on a similar look to states like Georgia and Massachusetts that have had statewide imports done. Another good example of what California can be is the Corine Land Cover.
Check out the [[California Land Cover]] wiki page to learn more.