Ashes are the remains of fire, they are the last stage of fire. You could use them to represent an end of a tragedy or passion spurt. In doing so you can represent a fall of an old order, the old hierarchy. Ashes on some one of power and or means can signify his loss of it. On the other side a character with little means and no power, can use this to signify redemption. A gauntlet he would run during those trying times would work as his repentance. Earning his reinstatement. In catholic tradition ash is used for marking an elevated class. A character marked with ash can represent him holding a higher status among the rest. If this is used, a wiseman or strongman must bestow it to give it credibility. At the end of the fire cycle, is the beginning of the life cycle. Ashes can be used, to show an equal and fertile beginning. In a flat field, blessed with ash,  trees need not to compete. If you show ash with embers, you can display a more active scene. A lively fire, a noble cause  being