In 2011 year StarCraft 2 players got an ability to create clans and groups (or maybe earlier, doesn't matter), which gave them an ability to personalize decals floating near their Command Centres, Hatcheries and Nexuses.
Custom decal is a small picture that is visible to all players in game matches and on loading screen. Basically it is your icon or portrait that can be customized via uploading ANY image.
Long time ago I created bunch of decals which you can use for free. Have fun!
