What ERC20 token are you mining?
There are many erc20 tokens that were made and it will be an ease if you will give the name of it and let's research it together if, there are those services or websites that you want to know that accepts it.
0xMR
Go to those casinos that have a support page for request like adding of new tokens or altcoins.
They would love to hear to your idea towards the addition of that erc20 token on their casino. But, it is better if you are the developer of it so that you can explain the technical aspect and give answer why they should add that.