Is it possible to display a robot model on top of the camera image in Rviz?

edit

If I understand you correctly, both are possible, although I'm not sure you'll end up with the result you are after.

Is it possible to show the camera image in the same [visualization frame] as robotmodel, TF, and markers? This might allow for the ability to skew the image to represent its state when it was taken.

Not with the standard RViz plugins, but @Stefan Kohlbrecher (in a recently answered similar question: Rviz: Display image in 3D scene) points to vigir_ocs_rviz_plugin_mesh_display_custom, which should be capable of what you want. You'll probably need to massage it a bit though.

Or, alternatively, can I display the robotmodel on the Camera frame?

I think this can be done using the Camera RViz panel. From the wiki page:

Creates a new rendering window from the perspective of a camera, and overlays the image on top of it.

This needs CameraInfo and (obviously) Image messages.