Most of them are, largely, already holidays, just under different names. Christmas/Halloween/Easter are all major pagan holidays, for instance. Most neo-pagan holidays are seasonal holidays, so I'm not sure which others would be available, really. Maybe a more important May Day?
Well...I have a hard time ascribing a religious sentiment towards holidays which through secularism have been shorn of nearly all of their religious symbolism. Personally I'd love to blithely honor St. Francis and Ganesha while engaging in public drunkenness/gluttony with not a modicum of belief entering the equation.