That is one reason why people often pay for a membership in a clipart site. They get to choose from a huge number of clipart designs for one small fee. It saves a lot of time, and if you have a bit of money that you could use to invest in a big time saver, then this would be a place to put it.
Do take the time to write a personality profile articulating the characteristics of your cartoon brand mascot. Write his life story. Tell your customers all about him. Flesh out his personality, and be sure he behaves consistently with who he/she is.
As their website mentions, "Many Flickr users have chosen to offer their work under a Creative Commons license, and you can browse or search through content under each type of license." Flickr is a major source of image for the open source community and helps in promoting the unfettered exchange of information over the internet. The WP Plugin called Wp-Inject assists you in searching for images on flickr and then adding them to your articles in a jiffy.