Why don't you simply hire a trusted campaign manager, escrow the funds and start a proper signature campaign where the manager should only accept the users you want for this to promote the ICO if you are willing to pay 100 of them? I think that would be a more better way of doing this than asking each and everyone to post their work along with their desired rates. You should allocate some rates for different ranks in the campaign and ask people to provide the links to their services in their applications and you will get what you are looking for.