I like the curtains and your idea for a sign at the top to fill in the gap. How roughed up do you want the curtains to be? I've used a metal parts cleaning brush to tear up shirts and fray cut edges. Even used a grill grate cleaning brush, with all the burnt stuff on there. You could also try staining the curtains in random spots with coffee, dry brushed paint or stain, RIT dye or india ink.