ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
placeholder.pics - Lightest way to include placeholder images in your design
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
PlaceKitten - Dead-easy placeholder images. Of kittens.
LightShot - The fastest way to take a customizable screenshot.
Fill Murray - Custom-sized placeholder images of Bill Murray