actually, it is not realy Nose art....the only Nose Art in the game is the Nose Art which is done on the skins made by HTC or by the Skinner Team or contributing individuals.......
what ou are refering to and are wanting to do is upload your squad patch or insignia which most times will show up under or near the cockpit on the sides of the fuselage.......
or on some bombers it shows up on the verticalStabilizer / tail section of the aircraft
to get an idea and to check the sizes allowed, you could look at the squads sub directory folder in your HTC/Aces High II folder/directory.....
although the helpfile shows it as being squad noseart.........