Before 2-D art, humans decorated their homes using space, time, and Carl Sagan. Celebrate one-dimensional artwork with today's Groupon: for $15, you get $30 worth of wall decals from SissyLittle.

SissyLittle's vinyl wall decals can cling to any smooth or semitextured surface, including walls, windows, and vacated tortoise shells. Fancy up plain façades with a hummingbird garden ($19.99), kitty cats ($23.99), or a counting caterpillar ideal for a child's playroom or toy manufacturer’s boardroom. All SissyLittle adhesives come with a squeegee and instructions for successful self-application. Working quickly, DIY decorators can personalize living quarters with starfish, swirls or Aztec borders ($23.99 each) or dress up portals to Narnia with custom designs cut from the cloth of original or existing decals. SissyLittle prides itself on delivering top-notch customer service and shipping its carefully packaged domestic U.S. cargo free of charge and passive-aggressive post-it notes.