Stock agencies that have vector images.
Stock Photography - Pixabay
Pixabay is a free resource that has photography, vector images, illustrations, and video for you to use in your creative...
Shutterstock is a well known name in the online stock photography world.  They have a wide variety of different types...
Stock Photography, iStockPhotos

iStockPhotos have a collection of royalty free images for you to license for your next project.

Stock Photography - Dreamstime
Dreamstime has over 58 million stock images to choose from, along with a large user community of over 17 million...
Stock Media, 123RF.com
A royalty free stock photo resource that has over 76,783,525 images to choose from.