I was reading in the advanced world generation notes about how you can get more biomes per area by messing about with the X/Y variations and such, so I decided to do a little test: all variants set to 1600x1600, max regions possible. Before long, I was setting everything to extremes. 554 rejects later, it decided to let me just accept the world, and it gave me... this.
There is so much strange with this world, it is mind-boggling. Deserts back miniature mountain ranges next to deciduous forests. Elevations are all over the map. There's at least 13 different oceans, most of them land-locked. I don't think there's a single open plain in the entire thing. There are no rivers, streams, or brooks. Words fail me in trying to describe what I'm looking at here. If you want to see the worldgen yourself, here you go.
[WORLD_GEN]
[TITLE:WILD VARIABLES]
[SEED:2978154016]
[HISTORY_SEED:1778253264]
[NAME_SEED:4033094240]
[DIM:129:129]
[END_YEAR:1050]
[BEAST_END_YEAR:200:80]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:1600:1600]
[RAINFALL:0:100:1600:1600]
[TEMPERATURE:30:70:1600:1600]
[DRAINAGE:0:100:1600:0]
[VOLCANISM:0:100:1600:1600]
[SAVAGERY:0:100:200:200]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[GOOD_SQ_COUNTS:25:251:503]
[EVIL_SQ_COUNTS:25:251:503]
[PEAK_NUMBER_MIN:12]
[OCEAN_EDGE_MIN:1]
[VOLCANO_MIN:10]
[REGION_COUNTS:SWAMP:1:1:1]
[REGION_COUNTS:DESERT:1040:1:1]
[REGION_COUNTS:FOREST:1:3:3]
[REGION_COUNTS:MOUNTAINS:1:2:2]
[REGION_COUNTS:OCEAN:1:1:1]
[REGION_COUNTS:GLACIER:1:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:1:3:3]
[REGION_COUNTS:HILLS:1:3:3]
[EROSION_CYCLE_COUNT:1]
[RIVER_MINS:0:0]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:25]
[NON_MOUNTAIN_CAVE_MIN:50]
[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:20]
[TOTAL_CIV_POPULATION:20000]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:1:1:1]
[RAIN_RANGES:1:1:1]
[DRAINAGE_RANGES:1:1:1]
[SAVAGERY_RANGES:1:1:1]
[VOLCANISM_RANGES:1:1:1]