A slightly different flavor. I use old Campy Nuvo Record and old Superbe Pro friction shifters as keychains. They weigh practically nothing, last forever, function as a keychain should (something to hold on to) and are a gentle reminder to yourself and those who care to pay attention that you have an interest/love for bikes.
That said, I think the crank arms and c-rings are OK... I would clean them up first. If you want to make it decoration, I would spray them in contrasting paint. Perhaps a bright gloss white to make them stand off the wall a bit. As they are,..... the old grease just does not look good.