Dear FireFox597,
Thank you for playing our game!
We are considering adding sound effects to the game in the future, for example a background OST. More types of sound effects will be considered in the future when we have more manpower/time to work as we develop.
Sprite change during battle is somewhat implemented via battle torn clothes when enemies are at low hp. We will see about how we can better improve this feature.
There is currently one art that goes with the NSFW scene implemented already in the game. You can find it when exploring the docks area. More arts are being discussed with the artists currently and might be added in the September update if everything goes well.
Hope this answers your question!