emplates?
Each aircraft has textures applied according to the modellers application; some textures are symetric (properly scaled: the image from the real aircraft can be scaled to fit without distortiions) while others are not. Since many were made with, basically, flat textures, there's often room for shading, seam lines, etc. -- but the original textures can be a general guide.

If repainting a default acft, the BAO program used 256 bitmapping so the texures can be viewed or edited with MSPaint (detail is limited, however, because more than one area of the plane is painted from sections of a single 256-color bitmap). Air Factory had its own texture format so you'd have to use a texture converter to view and edit in bitmap; many AF designed models are not symetrically textured so your applied texture looks squashed in one direction and stretched in the other. For me it's easiest to use a px of the actual acft as a guide, then resize my basic texture to fit the original AF texture (usually, particularly since I like to add in shading and seam lines, I still have to do some section alignment and touch-up afterwards).