Raster data sources are commonly used to read satellite imagery, scanned maps, and digital elevation model (DEM). You can add this data as a base layer for your maps.
ArcGrid is a proprietary binary format created by ESRI and used with ArcGIS. A sample is included with GeoServer. Check out the arcGridSample
data store and the nurc:Arc_Sample
layer.
A TIFF file is commonly used as the storage format for an aerial picture. A GeoTiff (http://trac.osgeo.org/geotiff) is an extension of the TIFF format. It includes Geospatial reference data in the header, an SRS, and the bounding box. Check out the sample data store called sf:sfdem
.