I set the maximum temperature to 600 in world gen. I've done it with 1000 maximum, and the results are basically the same. I still get live animals from caravans, too.
If you want something really awesome, turn the minimum temp to -1000 and the max to 75. The world is a blue black tundra, interspersed with forests and mountains.
Or you can turn the max to 1000 and the minimum to -1000, and you'll get a starry field of icy wasteland with mountain-encapsulated regions with warm temperatures. I even have a tropical moist broadleaf forest in one of these worlds.
If you have problems with worldgen not placing a dwarven civ, add to the initial forest count.
Oh yeah, if you really want tropics, fool with rain and drainage.
Also, I've just got to say this; I highly recommend Tropical Dry Forests. The wood types are refreshing, there are wet and dry seasons, and the main fauna?
Elephants.
Plump, juicy elephants. Seriously, I have three guys churning out wooden barrels, and about half of my huge food stockpile is filled with stacks of unbarreled elephant meat.
All from one hunter, who started as a cheese maker.
Plus, you'll get lungfish, which are really cool.
Edit: Those humans are offering me whale shark leather, siamang leather, manta ray leather, rubber tree logs, kapok logs, cacao, etc. But no traditionally temperate logs, except pine, cedar, and willow.
So now I know there's a tropical ocean somewhere on here. Should I upload the world for those of you who don't want to try and get lucky with worldgen?