My understanging is that Windows Mobile does not support Image Services.
It does support Map Services. Subtle difference - if you look at the REST endpoint in ArcGIS Server, you will not they are defined as either Map Service or an Image Service.
You can place your images in a map document, and serve the map document as a Map Service. To make it faster, you can create a cache, and therefore have a cached Map Service. Windows Mobile will support this.
If you have a cached tile dataset, ArcMap can view this as a raster datasource, so you can add the tile cache, to the map document as a raster layer, and then serve this as a Map Service. If the one tile cache is the only layer in the document, you can create a cache of the Map Service, and just copy the layers of data from the tile cache, into the service cache .....