This is my first attempt at a repaint and given that the textures are freeware I hope you'll forgive any mistakes!
I haven't been able to figure out how to add a text logo to my repaint so the textures
are just the paint and flags of the British Airways Union Flag livery.
To install the textures
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Create a directory in your flight sim's AIRCRAFT\b747_400 directory. Call it Texture.n (where n is the next availbable number - you'll already have some other directories there).
Next open the AIRCRAFT.CFG file in the AIRCRAFT\b747_400 directory and add the following.
Note that the title [fltsim.n] should have the same name as the directory you just created so replace the n with whatever number you used. You'll also need to use that number in the texture=n line.