DJ Khaled and Mayweather had an issue about shilling an ICO. And other celebrities hyping or promoting scam coins. Who would actually rely on their words? If you're listening to celebs then you are not ready for this type of market at all.
Celebs are certainly bad for ICOs in my opinion. They can only be helpful if the coins are already established like Eth or Xrp. I'm very sure that in the future when mainstream adoption of cryptocurrencies has happened, a lot of celebrities, models or hollywood actors will shill their own tokens in the ads.
It is not that they are bad but I don't think Celebrities will just accept it like that.
There are a lot of ways to advertise cryptocurrencies especially the new ones since there are a lot of sites, forums, and platforms that posted these things and there are also, obviously a lot of people there looking up into it. Why would you pay a Celebrity to advertise your coin if you can just (for example) start a Signature Campaign here in the forum? They are Celebrities and that means a lot of people are ready to watch him or her but with a huge talent fee of course. Even if you pay them huge money, I don't think they will say yes that easily as we all know how cryptocurrencies are viewed these days.