Food trucks don't exist in a vacuum: They always operate near other businesses, and the people who run these trucks have to keep this in mind. Custom vehicle wraps that are too similar to surrounding businesses will confuse customers.
The Washington Post recently featured an article on the way food trucks on the National Mall are clashing with the stands that are already there. Since many local vendors have maintained the same location for years, the incoming trucks seem like hostile invaders.
However, the truck drivers see it exactly the opposite: They feel they should have the right to vend in the area despite what longtime business-owners there think. The source spoke to truck co-owner Doug Povich about the need for proper recognition on the Mall. He says that the vendors currently working there don't allow for outside competition.
"It's this little monopoly on street food and souvenirs down on the Mall, which results in nothing that is good for the consumer or good for the impression that the city is giving to visitors," Povich said.
Food trucks should prepare for this by studying what stands are stationed where and adjusting their truck accordingly. If your truck is planning to sell a food similar to those other stands are already selling, then you can think of imagery that sets it apart and makes it clear to customers what the difference will be.
For example, fairs and festivals commonly sell junky foods like hot dogs and burgers. In the case of events like the York Fair in Pennsylvania, there might be more unusual foods like "deep fried peanut butter and jelly sandwiches" available.
By knowing what's already at the venues you're interested in, your business will be more likely to improve.