As an example, we previously had the following work done:
Ideally, mockups would be on buses that are in a real-world setting like this, as well as the images attached:
In the examples above, After1 is is the closest to what we are looking for. Ideally, this would be a straight side-view (not skewed), and even more realistic.
We have attached several raw images for you to use, although we recommend going with the side-view. You can also take a look at our Instagram feed, and if you see anything there you want to use, we may have a higher-res version:
Finally, to get ideas and creative imagery for various advertisers, we recommend searching the internet. Some brands we would recommend are Heineken, Corona, Red Bull, Vita Coco, Vitamin Water, Bacardi Rum, Malibu Rum, Captain Morgan's, Absolut Vodka. Try image searching "Brand Name + Bus Wrap", for example: