Photopea is a new Chrome App that I learned about from The Tech In blog. Photopea allows you to open and edit Photoshop and Gimp file formats (PSD, XCF, PSB, and conversions) on a Chromebook. This opens up even more functionality to Chromebooks.
Photopea is not as full featured as Photoshop or some other apps, but it offers the basics, which is all most people need. It is built with HTML5 and supports layers, layer styles, levels, curves and much more. You can also use it to convert images between JPG, PNG and WebP formats.
Resources to get Started With Google Apps and Chromebooks
Google Apps and Chromebooks Web App Recommendations - a whole lot!
Great, free Image editing sites and software
Two Free Graphic creation and editing software
PicMonkey - free online photo editing
Two More Free Image Editing Resources