The themes of adult coloring books are usually intricate and centered more around adult images, not your childhood counterparts that included bunnies, super heroes, and farm animals. You would expect to see geometric patterns, psychedelic patterns reminiscent of doodle art type pages, fantasy images including angels, dragons, goddesses and mermaids, and ancient designs of religious and spiritual nature.
Think about it this way; would you rather spend about an hours looking over and printing out SpongeBob coloring pages, or would you prefer to drive all over the place looking for a SpongeBob coloring book? The answer to this really depends upon whether the website, or websites, you are visiting have the coloring pages of SpongeBob Squarepants that you really want. Chances are that the website/websites that you decide to look on will have the images that you are looking for; yet you might not always find what you are looking for out there. Do you realize that you can have as much fun looking for the SpongeBob coloring pages that you want as you will when you sit down to actually color those pages?