This was posted a while ago but in case you're still interested, I made 2 hugel beds last year with conifers and eucalypts.
I didn't have anything huge, the largest pieces were around 20cm thick and maybe a little longer (older dry stumps), the logs about 15cm circumference and 2.5m long (recently cut). Lots of smaller Eucalyptus branches plus leaves, the Cupressocyparis mostly from 3m high young trees, needles and all. Also used some smaller lillypilly branches. No sign of termites so far (it's been more than a year) but plenty of garden ants. The two beds were the only green section at my place last summer and they got no more water than anything else, less than the fruit trees, and the growth was awesome. Lots of beans and grapes.
I've redesigned the whole area and will be taking these beds apart in the next couple of months, it should be interesting to see if much has decomposed - it was very dry up till last month so I'm guessing not much!
My initial attempt at raised beds with Eucalyptus prunings has settled a lot but there's no sign of the leaves anymore. Protea flowers and worms, yes, tree leaves, no. Lots of happy apple tree growth and the comfrey plants were massive, even with the lack of water. I didn't shred the leaves or even break the branches up much before I put the bed together, so I'd say Eucalypts are definitely worth using. Particularly if that's mostly what you have!