Sydney is a really nice and photogenic city. We had luck that at the time we visited, the Vivid Sydney took part where lot's of buildings were illuminated in different colours.
Byron Bay is really worth a visit. Nice summer feeling, long beaches and the most eastern point of Australia including this picturesque lighthouse which is especially at sunrise really stunning. And if you are lucky you can see dolphins jumping around in the sea below.
You shouldn't miss Magnetic Island if you wanna see koalas or wallabies. And in addition you get a beautiful coast and nice, sometimes a bit, but not too extreme, touristic villages.
The blue mountains are not far away from Sydney and a nice trip for the weekend (or any other days of the week). We did some nice hikes, managed a lot of steps to get down to the valley and then back up again (and then down again and up). It was a bit cold, especially at night (about 3°C). But during the day when the sun came out it was good.
Because I had some time left I stayed quite long in Nossa. But it woas propably the best I could do. The Noosa Nationalpark is one, when not the best, nationalpark I visited during my journey. The coast and the beaches are gorgeous. And if you are lucky you can spot a koala or a wallaby.