This Thumbnails icon is made in Material Design style developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 4,400 icons, all in the same style and quality.
The logo is of a series of nine small squares in a grid pattern. The grid is three squares wide by three squares tall. The squares are not touching at all, there is an even amount of space between each square.