When using QLandkarte GT you need maps. Usually you have to buy maps. Free digital raster maps are rare. Commercial ones have very strict copyrights and proprietary formats. Due to very strict laws in the free western world it's close to impossible to discuss these formats without spending money on a lawyer.

• A possible source of maps are scanned paper maps. QLandkarte GT offers a nice tool to reference scanned maps. Have a look at the (F1) "Map..."  menu.  (F6) "Edit / Create Map" will offer you a referencing dialog.
• To use the 3D gadgets you need elevation data. A nice collection is here.
• Another source are maps for OZI Explorer. There is a script at  http://sourceforge.net/projects/ozi2geotiff that converts your OZI maps into geotiffs. 
• The OSM project is also a nice source of maps. QLandkarte GT supports these maps as Garmin *tdb/*img map file collection. As mobile device you need a Garmin GPS.
• There are nice mountain bike and hiking maps for Garmin devices derived from the Open Street Map project on openmtbmap.org