I wanted FBReader on Ubuntu to match the native Ambiance theme & Humanity icon set in 13.04 (Raring). So I put this together. Uploading here in case anyone else wants to use it.

Icons replace the existing ones in /usr/share/pixmaps/FBReader
(may vary by distro)

If you want to use the included Unity-friendly app icon, move FBReader.png one folder up, to the pixmaps directory. It will replace the existing icon.