Umm.. You don't have any gap to fill in.
"Linus likes penguins". That's it. There was even a headline on it in
some Linux Journal some time ago (I was bitten by a Killer Penguin in
Australia - I'm not kidding). Penguins are fun.
As to why use a penguin as a logo? No good reason, really. But a logo
doesn't really ave to _mean_ anything - it's the association that counts.
And I can think of many worse things than have linux being associated
with penguins.
Having a penguin as a logo also gives more freedom to people wanting to
use linux-related material: instead of being firmly fixed with a specific
logo (the triangle, or just "Linux 2.0" or some other abstract thing),
using something like a penguin gives people the chance to make
modifications that are still recognizable.
So you can have a real live penguin on a CD cover, for example, and
people will get the association. Or you can have a penguin that does
something specific (a Penguin writing on wordperfect for the WP Linux CD,
whatever - you get the idea).
Compare that to a more abstract logo (like the windows logo - it's not a
bad logo in itself). You can't really do anything with a logo like that.
It just "is".
Anyway, go to "http://www.isc.tamu.edu/~lewing/linux/" for some nice
examples..
Linus