Hi Pedro,
Unbelievably, I did a soundcheck with Maiden back in '81 at the Edinburgh Odeon (Killers tour, loooong story).
The line drawing IS definitely basic, the actual painting of camo I'll go with will be a hybrid of the images below.
Given that Stigler worked with the artist in the 'Higher Call' painting signed off on it, I'm guessing he's ok on the detail, so a lot of the painting will be based on this work...
If you have anything on this bird, please share!
1 additional image. Click to enlarge.