No cash money tips can be accepted by any slot or casino host. It's too much like a bribe as they are the ones who determine whether or not you get that free room or comped meal. However, you can give them gifts. I like food items from my local area like an assortment of jams, or a nice bottle of wine. Also acceptable are things like scarves, ties, lapel pins, tie clips, candy, etc.
Gift certificates are a grey area.
Some casinos are okay with them, others frown upon it. Another nice thing to do is to send flowers or a plant, but the best thing you can do according to the slot hosts I spoke with is to write a very nice letter to their boss letting them know how well you were treated and how much the assistance of your host contributed to the wonderful time you had in their casino. I do not feel a need to tip the change people who come around to fill the hopper or count out any hand pay jackpot that I get. If a change person was helpful in finding a particular game or getting bills to work in the machine that results in a win, I will share. However, there are a number of times I don't have any contact with a change person.