Not exactly sure what your driving at. Do they need an official logo? Yes. Has it been developed yet? no.
Yes, a good logo can help. But can it help so much in a election system like yours that is geared (as I understand it) for just two parties that are essentially big tent parties/coalitions of many groups?
I mean, have third parties any hope in your kind of system? Except maybe taking away voters from the big party that has agendas closer to yours? And thus giving the other party the victory?
Or are there some features about your countries system that I don´t know about that make it good to have a third party, instead of say an organization, pressure group or something like that within or outside of the current party structure?