This thread, you mean?It's fine to start a new thread like this; I wouldn't worry about it. There are enough replies already to warrant the separate thread, I think. If you really, really want to move it, though, let me know and I can do it for you.
For future reference: when you're viewing a thread like "Portrait Gallery" (or any thread), if you want to reply in that same thread, press the "Add reply" button. If, on the other hand, you want to start a completely new thread, then press "New Topic". In this case you must've pressed the latter.