Mokkup - Create Stunning Dashboard Mocks in Minutes!
Visual Hunt - We hunt free high quality stock photos.
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
Pixabay - Over 270,000 free photos, vectors and art illustrations
MockFlow - A super easy wireframing tool with all the other tools you need in the product design process
Yay Images - Get unlimited stock video & image downloads.