Some good resources for web game development

Websites to compress images

https://tinypng.com/

https://www.websiteplanet.com/webtools/imagecompressor/

Create spritesheets online for HTML5 games

https://www.leshylabs.com/apps/sstool/

Create Android assets online

https://romannurik.github.io/AndroidAssetStudio

https://easyappicon.com/

Royalty free images / vectors

https://pixabay.com/

https://www.pexels.com/

https://publicdomainvectors.org/

https://openclipart.org

https://purepng.com

https://www.iconspng.com/

Free custom icons

https://www.iconsdb.com/

Online APK Analyzer

https://www.sisik.eu/apk-tool

Free Icons for Commercial Use

https://iconarchive.com/

http://www.iconsdb.com

Generate CSS Sprites

https://instantsprite.com/

Responsive CSS Sprite Maker

https://responsive-css.spritegen.com/

Free Sound

https://www.freesound.org