Not quite like necromancer I think there should be silver and gold badges for answering a number of questions (5/50) that previously have been "awarded" the tumbleweed status.
This might require that questions get automagically tagged with a system tag called tumbleweed so that people can find these kind of questions.
Just because I didn't get an answer doesn't mean I'd wouldn't appreciate one even 1 year later. I know one might say that "why should I answer a question so late if there's no guarantee for an acceptance?" etc, but I guess you can choose to do so based on the "askers" profile.
Thanks for your time
Edit I guess you can find these questions by clicking on the tumbleweed badge as Borror0 pointed out, but might not be as obvious as searching for a tumbleweed tag. Still my badge request/suggestion remains