Gimp
https://www.gimp.org
Free open source image editing software.

Google Reverse Image Search
https://images.google.com
Search an image by dragging it into the search bar.

Pixabay
https://pixabay.com
Access images and videos free of copyrights or royalties. All images and videos are made available thanks to Creative Commons CC0.

Pixlr
pixlr.com
Free online photo editor.