Xanthoparmelia is plausible and, probabilistically, a good suggestion, for there are about 80 species of the genus recorded for the ACT (or nearby). So, if you wanted to bet on Xanthoparmelia, you'd have a good chance of getting your money back. However, there are other genera of Parmeliaceae in our area, though not with so many species as Xanthoparmelia. A Parmeliaceae expert has told me that, in general, he is very wary of identifying Parmeliaceae based just on photos. Hence, I leave these things at family.