I just want to briefly list some helpful links to image services that I came across the other day.

Flaticon: https://www.flaticon.com/

Flaticon is the largest search engine of free icons in the world.

Giphy: https://giphy.com/

Giphy is a website that provides lots of gifs. There also exists a public API that allows to search for gifs and embed their url in your website.

Public API: http://api.giphy.com/v1/gifs/search?api_key=dc6zaTOxFJmzC&limit=1&q=yourSearchTerm

Placeimg: https://placeimg.com/

Placeimg provides placeholder images for your project in progress. Custom URLs generate placeholder pictures in various sizes with categories and effects.