The FDO Provider for ArcSDE is based on a subset of the ArcSDE API. This subset does not include the following:

Raster functionality
Native ArcSDE metadata
The annotation data, with the exception of the ANNO_TEXT column

http://wikihelp.autodesk.com/AutoCAD_Map_3D/enu/2013/Help/0005-FDO_Deve0/0104-OSGeo_FD104/0109-FDO_Prov109

use WMS service as Brad Nesom mentions

The FDO Provider for ArcSDE is based on a subset of the ArcSDE API. This subset does not include the following:

Raster functionality
Native ArcSDE metadata
The annotation data, with the exception of the ANNO_TEXT column

https://knowledge.autodesk.com/support/autocad-civil-3d/troubleshooting/caas/sfdcarticles/sfdcarticles/Connecting-to-ArcSDE-ArcGIS-Raster.html

use WMS service as Brad Nesom mentions