https://github.com/cpetry/TextureGenerator-Online

https://github.com/cpetry/NormalMap-Online

They're both MIT/Expat-licensed. You can download it and run index.html, it will work (it's fully client-side), but you can also use this:

http://cpetry.github.io/TextureGenerator-Online/

http://cpetry.github.io/NormalMap-Online/

Normal maps, parallax maps, specular maps and ambient occlusion maps can be created and tweaked.