1. A method comprising: receiving an image geometry for an image within a graphics processing unit (GPU) pipeline included in a GPU; storing attributes for vertices within the image geometry in an extended vertex cache coupled to the GPU pipeline; and processing the image within the GPU pipeline based on vertex coordinates that identify the vertices and vertex cache index values that indicate storage locations within the extended vertex cache, the storage locations storing attributes of the vertices within the image geometry, wherein the vertex cache index values that indicate storage locations in the extended vertex cache are passed to processing stages along the GPU pipeline, the vertex cache index value that is passed along the GPU pipeline to a processing stage of the GPU pipeline for use by the processing stage to retrieve an attribute stored at the location in the extended vertex cache indicated by the vertex cache index value.