By the 'reaper' do you mean Death? If so you can dedicate an altar to him with things that represent death. If I was honoring the Grim Reaper (or Death) I would probably include an image of him, a statue or portrait. I would add some black candles as well. Anything that reminds you of him or that you think he would be pleased with.
I would probably do some research on other things that might be associated with him.