Okay, I managed to create a world with a site I like: A terrifying (!?!?!?!), freezing tropical moist broadleaf forest, savage (untamed wilds) glacier and tundra, and a magma pipe.
God help us all. Here are the parameters:
Created in DF v0.28.181.40d.
[WORLD_GEN]
[TITLE:WEIRDTEMP]
[SEED:3017843167]
[HISTORY_SEED:3522223109]
[NAME_SEED:2960373252]
[DIM:257:257]
[END_YEAR:1050]
[BEAST_END_YEAR:600:80]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:1]
[ELEVATION:1:400:1200:1200]
[RAINFALL:0:100:1200:1200]
[TEMPERATURE:-200:225:1200:1200]
[DRAINAGE:0:100:1200:1200]
[VOLCANISM:0:100:700:700]
[SAVAGERY:10:100:1000:1000]
[ELEVATION_FREQUENCY:4:1000:9000:9000:120:300]
[RAIN_FREQUENCY:3:1:2:4:7:8]
[DRAINAGE_FREQUENCY:3:1:2:6:5:4]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:4:5:2:10:25:65]
[VOLCANISM_FREQUENCY:4:50:5:2:15:75]
[GOOD_SQ_COUNTS:150:1500:3000]
[EVIL_SQ_COUNTS:75:750:1500]
[PEAK_NUMBER_MIN:6]
[OCEAN_EDGE_MIN:2]
[VOLCANO_MIN:200]
[REGION_COUNTS:SWAMP:1:1:1]
[REGION_COUNTS:DESERT:1:1:1]
[REGION_COUNTS:FOREST:200:13:12]
[REGION_COUNTS:MOUNTAINS:500:8:8]
[REGION_COUNTS:OCEAN:1:5:5]
[REGION_COUNTS:GLACIER:1:1:1]
[REGION_COUNTS:TUNDRA:1:1:1]
[REGION_COUNTS:GRASSLAND:1:1:1]
[REGION_COUNTS:HILLS:1:1:1]
[EROSION_CYCLE_COUNT:75]
[RIVER_MINS:450:450]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:40]
[MOUNTAIN_CAVE_MIN:175]
[NON_MOUNTAIN_CAVE_MIN:515]
[ALL_CAVES_VISIBLE:1]
[SHOW_EMBARK_RIVER:2]
[SHOW_EMBARK_POOL:2]
[SHOW_EMBARK_M_POOL:2]
[SHOW_EMBARK_M_PIPE:2]
[SHOW_EMBARK_CHASM:2]
[SHOW_EMBARK_PIT:2]
[SHOW_EMBARK_OTHER:2]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:40]
[TOTAL_CIV_POPULATION:20000]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:5500:16512:3400]
[RAIN_RANGES:8256:16512:8256]
[DRAINAGE_RANGES:8256:16512:8256]
[SAVAGERY_RANGES:8256:16512:8256]
[VOLCANISM_RANGES:8256:16512:8256]
The world is strange, and has lots of clustered volcanoes, caves, and odd elevations/temperatures/everything. Some good civilizations; these parameters make a lot of forests/plains areas for elves and humans to fight it out, and just enough mountains to get at least some dwarves. I made sure the parameters allow for just about every type of biome and such, and is heavily waited towards what I'll call "weird shit". I had to bump max subregion count up to maximum because of how variable all the geographical details are.
The embark location I was talking about is in the southwest; look for a single glacier tile in a big evil (should appear grey/red?) forest. Also, if you look at the north end of the glacier instead, you can get an embark site with mountain features (I think I saw a couple magma features, a cave, and a chasm?), while retaining some of the ones I was just talking about. And the mountain is good+savage, which is pretty interesting I guess, especially if you've also got the terrifying forest in there.
Also, if you aren't looking for that type of site at all, the world might still be interesting, since it has a bit of everything, usually five feet away from everything else.
Warning: I haven't embarked yet, so I have no idea if everybody will freeze to death immediately upon going to that area. But it's near ENOUGH to some plain old "Cold" areas, so I doubt it's that bad.
[EDIT]
Don't be fooled. Those params/seeds will cause two or three rejects before making the actual world; it's normal.