I think Crux Frost is about the biggest map you'll get (slightly larger than Crux Whirlwind, which could also be considered). Although not quite as big as the other two, TPW Strangewood Mire or my own work DF Atlas could be fun as well. There's plenty of other fun high quality maps playable as FFA / 2v2 available, just search for some of the following mapmaking team tags on battle.net: DF ESV TPW KTV AEM Crux. I hope you'll find something that fits your needs.
edit: If you're looking for real madness, Crux Breeze might be what you're looking for.
I think Crux Frost is about the biggest map you'll get (slightly larger than Crux Whirlwind, which could also be considered). Although not quite as big as the other two, TPW Strangewood Mire or my own work DF Atlas could be fun as well. There's plenty of other fun high quality maps playable as FFA / 2v2 available, just search for some of the following mapmaking team tags on battle.net: DF ESV TPW KTV AEM Crux. I hope you'll find something that fits your needs.
edit: If you're looking for real madness, Crux Breeze might be what you're looking for.