The airline logo's are standard Windows bitmaps at a size of 76 x 16 pixels. They are stored in the following directory:
C:/Program Files/AirNav Systems/AirNav Radarbox 2008/Data/Logos
The logo should be named to match the ICAO Flight ID shown in the RadarBox aircraft lists, so to show the logo for British Airways aircraft, for example BAW123 - then the logo should be named BAW.bmp (the BAW.bmp logo is already included with RadarBox - this is just shown here as an example of how logo's work).
For new and updated logo's, see the following thread:
http://www.airnavsystems.com/forum/index.php?topic=682.0