Generally, the amount of visitors you receive depends on how well you manage to meet their needs and demands. Enclosures and animals only help generate a certain amount of potential visitors. If their needs aren't met, you will lose them again.
Stalls, garbage cans and restrooms won't attract new visitors, but if these manage to help meet your visitors' needs, then they will get visitors to your zoo, too. This will only happen if your visitors' needs aren't over-achieved, however.
And of course, visitors prefer to see happy, healthy animals - so make sure to take care of their needs, too!