Hi,
I don't know of an easy way to do this, but after my setup, it is very easy for me to add raster maps to my projects.
Here's how it works in theory.
1) Integrate your own DLL into ArcGIS Mobile
2) The code will be simple, look at target directory on the computer, if there are folders in them with a conf file, consider it as a raster image and load it into the application.
3) To create a raster image suitable for ArcGIS Mobile, I have a 12 step manual on how to do this. Also this solution will only work if you have physical access to the computers, because you will need to physically place the raster maps into the directory on each computer.
For example, I have 6 tablet PCs, if all them require a high resolution raster image of the Empire State building and the roads surrounding it, I would follow my 12 step procedure on creating a raster tile cache. Then go to each tablet PC and copy the tile cache in the designated folder. In this case the folder name is "Local Basemaps". When the user launches ArcGIS Mobile, my code will look at the folder, find if a folder within it has a conf file, and assume it is a raster tile cache and load it in.
I only allow basemaps to be add to ArcGIS Mobile when it first launches, I don't allow hot swapping of basemaps.
I am also able to distinguish between Raster and Vector maps added this way, so I can add special vector layers like Fishnets to create a grid like data collection method.
If you are interested in more details please post here.