Style Tiles.

Style Tiles are a design deliverable consisting of fonts, colors and interface elements that communicate the essence of a visual brand for the web.

Style Tiles: The Flip Side of WireframesDesign Shack
Style TilesStyle Tiles
Designer’s Guide to Working With Style Guides & Style TilesHongkiatSeptember 1st, 2016
Style Tiles and How They WorkA List ApartMarch 27th, 2012