There are plenty of images that are easy to edit, especially if you have image editing software.
However, there is a site that makes it even easier. They have 8 stock images, and you can simply type in the text that you want to appear in the images. You can save them and add them to PowerPoint presentations and other things like that.
The site includes the ability to add custom text to things like a magic eight ball, George W. Bush, and other images, and is completely free to use.