Great pics! I lived in Darwin for a couple of years, can't say I miss the weather! But the scenery is fantastic, the sunsets are something to behold (head down to the Casuarina Markets just on the beach at sunset) and the tropical storms are fantastic (loved the sheet lightning across the clouds). I should really go back someday.
If you are heading down to Alice Springs, I'd highly recommend dropping into Mataranka, it's about 100km's south of Katherine along the Sturt Highway. It's got some beautiful and relaxing natural thermal pools situated next to some camp grounds. Well worth the visit.
http://www.ourterritory.com/katherin.../mataranka.htm