Here are some examples of variables.

 

This picture is just some black coloring and straight and curved lines. The two figures do not look like humans, because their heads aren't even attached to their bodies! We know that this restroom is accessible for males and females because each picture represents the two genders. The figures could be considered variables.

 

This would be another example of a variable. It is just circle with a large X going through the center with two R's on either side. It looks nothing like a train or even a train crossing, but once again, it represents train crossing.