I have 2 ideas for you. If DH's aunt had a particular favorite flower, maybe a small vase of that particluar flower? It wouldn't need to be up by the casket, it could be on one of the tables, or on the stand where people sign the book. The other idea is to call the funeral director, to see if they know which florist the family is using, call that florist and ask their hlep in getting something to coordinate with what the family is doing.