Not that it's a complete cut and paste job (though I do do a lot of that). I do a lot of color, hue and saturation balancing, brightness and contrast adjustment, artifact removal. I also add layered drop shadows to most elements to help them stand out.
Sometimes I do some minor reconstructive work. For example, I could not (and still cannot) find a scan of the SO1 artwork that does not have part of it blocked by a sticker, so I just filled in the gap there.
For Wing Commander 4, the logo was pretty much in tatters after I extracted it from the box art, so I completely reconstructed it -- the IV by my own hand in GIMP, Wing Commander text from the Armada high resolution art, TPOF text from the high resolution scanned manual. Then I used that original extracted logo as a template for sizing and positioning.
For the Proving Grounds icon, I rendered the "Proving Grounds" text in GIMP, reshaping the I, U and S to match the appearance of the title art. It uses another piece of Armada high resolution art. I'll probably most likely come back to redo this one later on, but what I have is a good start.
I do use some in-game text from time to time. The text on the smaller Armada icons, as well as the VotK subtitle on the 256px WC2 icon are both from in-game screenshots.
So, yeah, I'm not redrawing these by hand or anything, and I'm not doing anything spectacular that nobody else could do -- it's just a passion for Wing Commander that spilled out through this creative outlet for me. Plus, I sure do love having big pretty icons to click on when I want to play a game. :>
By the way, if anyone has any ideas or suggestions (or criticism!) for these icon sets, I'd love to hear it.
Does anyone think it would be worth making a SWC iconset in this style? I don't know how Mac OS Classic icons work, or the state of Classic emulators on PC.