1. A system, comprising: a virtual compute instance, wherein the virtual compute instance is implemented using central processing unit (CPU) resources and memory resources of a physical compute instance, wherein the virtual compute instance is provided by a multi-tenant provider network, wherein the virtual compute instance comprises a first graphics library comprising a first set of graphics functions, wherein the virtual compute instance comprises an intermediate driver configured to translate calls to the first set of graphics functions to calls to a second set of graphics functions associated with a second graphics library, wherein the second graphics library provides the second set of graphics functions to one or more applications executing on the virtual compute instance, and wherein the second set of graphics functions differs at least in part from the first set of graphics functions; and a virtual graphics processing unit (GPU) attached to the virtual compute instance over a network, wherein the virtual GPU is implemented using a physical GPU, wherein the virtual GPU is provided by the multi-tenant provider network, and wherein the virtual GPU implements the second set of graphics functions associated with the second graphics library; wherein the virtual compute instance executes an application, wherein the application issues one or more calls to the first graphics library, wherein the intermediate driver translates the one or more calls to one or more equivalent calls to the second graphics library, wherein the virtual compute instance sends the one or more equivalent calls to the virtual GPU over the network, wherein the virtual GPU executes the one or more equivalent calls using a driver associated with the second graphics library, and wherein the virtual GPU generates graphics output based at least in part on execution of the one or more equivalent calls.