You don't have to include a screenshot in the distributable. Try to keep it as tight as possible. I think the extensions shouldn't call enable() and disable() itself and shouldn't do anything if it is disabled. There are other mechanisms to reload your settings if you extract your methods. If I see it correctly, when I start the settings dialogue via gnome-shell-extension-prefs and change something, the extension enables itself, right? That shouldn't be the case, I'd say.