You can use Variables, Display Conditions and Actions to make an asset appear after an Audio asset has completed playing. Here's how;
1. Create a Variable with a Default Value set as No
2. Add an Action to an Audio asset that updates the value of the variable to be Yes
3. Add a Display Condition to the assets you want to hide so that they will only display when the value of the Variable is set to Yes
Result: when the audio file completes the assets will display