Where place own application icons? How to get the current theme icons?

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http://unix.stackexchange.com – I'm developing a little application for Gnome, Unity and KDE desktops. I want the application icons to be fully theme aware. Now, I'm including the icons on the application directory on /usr/lib/my-application/ as SVG, and I'm loading them with the full path. I suppose this is fine as the start point, but I want to integrate them on the system better. My motivation: I don't want to break the Humanity and Humanity-Dark themes --very worried about the Indicator panel looks. How do I provide Humanity and Humanity-dark icons? How do I know the current theme? Should I ask for it? I'm using mostl (HowTos)