The Application Logo on the upper taskbar

I have no idea, I don't even know where to remotely start, I'm assuming I'll have to do some command line?

As far as I know, there is no simple click-and-change interface for this.
The icon used is called distributor-logo and is in the XXX/places directories of the applicable icon set.

For instance, if you are using the Human theme (the default Ubuntu theme), you will find these in /usr/share/icons/Human/scalable/places, /usr/share/icons/Human/48x48/places,
/usr/share/icons/Human/24x24/places etc.

Note that in this case these are symlinks to the start-here icon. Changing this icon (with su privileges) will change the logo (you obviously need to restart for this to take place).

Which icon will be changed depends on which icon is being used, which depends on the size of the panel (mine is 24 and the 24x24 icon is used).

Note also that the scalable icon must be a valid 128x128 svg icon while the others can (must?) be in png format.

Hello !

You should find valuable informations here : http://www.gnome-look.org/content/show.php?content=42926

Hope this helps !

Regards,
Benoît

I should add that for experimentation is perhaps better to clone the icon set you intend to change, and set it in use with System->Preferences->Theme->Customise->Icons