yeah, depends on what you like. Like if you like Harry potter, Percy Jackson, Hunger games or any other series, Google images offers awesome cover pics on the themes. If you like cricket, you can put up a cover pic of the team- ALL from google images!
There are websites such as http://www.iwantcovers.com/. The website have different pictures and messages depending on your choices. When you select the covers that you want, you click on it and gives you an option to upload.