On occasion, I’ve needed to put images in things like readmes and wikis on GitHub. I don’t have a go-to image sharing website, but GitHub will host images for you if you drop them into the comment form on an issue. So, when I need to use an image elsewhere on their website, I drop it into the comment form. I let it upload, then copy the link. I don’t post the comment, but I use the resulting URL (something like https://cloud.githubusercontent.com/assets/291371/3639183/ec126d50-1070-11e4-876f-e3cd692756ac.png) where it is needed. GitHub probably doesn’t want you using these URLs elsewhere, though, so if you do, I didn’t tell you to.