This is the only help I can find in the online documentation Daniel Fenton
Does ArcGIS Open Data support imagery and raster data?
Yes. Imagery and raster data must be registered as Image Services to be added to Open Data. Open Data does not currently support raster layers within a Map Service.
What this doesn't really tell me is how the image service needs to be configured....
I've found a few image services in the ArcGIS Open Data site but they all seem to be mosaic datasets. Is it possible to share raster data through an image service?