there are more, but those are what i can think of at the top of my head.
paint.net is superior to paint in almost every way, but inferior to photoshop.
Photopea Online Photo Editor lets you edit photos, apply effects, filters, add text, crop or resize pictures. Do Online Photo Editing in your browser for free!
www.photopea.com
Basically photoshop online and perfect for sign creation (As long as you're not making replicas of Da Vinci's paintings)