Answer
ArcPad directly supports the use of the following raster image formats: JPEG, MrSID (compressed images), Windows Bitmap, and CADRG raster maps.
ArcPad requires an associated world file for supported image formats. World files provide georeferencing information for the image. The image should also have an associated projection (.prj) file.
The .tif file format is not directly supported with ArcPad 6.0.3. It is possible to export TIFF images from ArcGIS ArcMap for use in ArcPad; the export process converts the TIFF images to MrSID images. When creating an MrSID image within ArcGIS, there is a size limit of 50MB (evaluated by the 50MB Rule which is actually 50 million cells). Therefore, ArcGIS cannot convert an image larger than 50MB into an MrSID.