Slayumind.org

Tools

Free, no sign-in needed: a QR code, a palette to check colours against, and the Media Editor.

QR code
A rounded QR code from text or a link, as PNG.
Palette
Build a palette and check whether colours fit it. I'll nudge the ones that don't.
Media Editor
Paint, build seamless textures, fix photos with effects and save as PNG. It runs in your browser, and your files stay with you.