Any area that has a lot of people partying in it is going to end up becoming quite dirty if you think about it. While a limo bus is generally going to give you a service that facilitates cleaning the bus once you are done, leaving the bus in such a state is poor etiquette. You need to show that you have good manners after all, and the only way in which you can do such a thing is by cleaning up after yourself and having a few other people take part in the cleaning process as well so that you are not the only one that is forced to perform this task.
A good idea when it comes to this sort of thing would be to stop for a meal once the party has winded down and have everyone get off. People would be hungry after all of that partying on their denver limo bus and going to a casual place where they can grab some food is going to be a great way to help them finish off what was undoubtedly one the most fun nights that they have ever had the privilege of experiencing.
Once everyone has gotten off, you and a couple of other people can at the very least pick up the trash that would have accumulated over the course of the party. Picking up trash and putting it in garbage bags would make the job of the person responsible for cleaning the bus easier. You can contribute to someone else being able to enjoy a less stressful day, and that in and of itself should be enough to encourage you to do your part in keeping the bus relatively clean.