placeholder.pics - Lightest way to include placeholder images in your design
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
PlaceKitten - Dead-easy placeholder images. Of kittens.
GIMP - GIMP is a multiplatform photo manipulation tool.
Fill Murray - Custom-sized placeholder images of Bill Murray
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.