As you only have 3 months to book your flights I'd suggest you wave goodbye to destinations like Sydney which usually book up 12 months out.
In any event, surely the best value is in spending the miles to go somewhere you actually want to visit ? Maybe that's just me though...
If you want some suggestions of good places to redeem which normally have fair availability:
* Narita (Tokyo)
* New York (hard to go wrong with this destination)
* San Francisco (sometimes tricky but if you're flexible with dates I think you'll get flights)
* Vancouver
BAH