I have been lucky to have departed from the dedicated A380 Terminal 3 a few times. As far as I recall the only spot you can get any photos of the A380 from is once you enter the departure lounge and even then the views of the A380 aren't that great. It all depends which gate the aircraft is parked at. There is one gate that gives you a sort of three quarter view of the A380, but definitely good for head on shots. As I said it all depends on the gate, some gates position the aircraft so that the airbridge blocks a good portion of the front of the aircraft as seen from the departure lounge.
Another thing to consider is time of departure. If it is daytime reflections might be a slight problem, more so at night.
I cant comment on taking photo's from other non A380 area's in T3
, it's been over a decade since I flew Air New Zealand on their B747- 400's.
You may have more luck when you arrive in Singapore, as you exit the aircraft, there are large windows that give you a view of the front of the A380, but I am not too sure what the Singapore authorities position is on taking photo's from airport boarding and disembarking areas.
Hope that helps.