These are custom billboards for the game Yoot Tower, the spiritual sequel to SimTower in the west. The game uses a plug-in system that would have allowed expansion of the game, but the English release saw little extra content produced for it. However, now you can at least enjoy some additional billboards for your towers.
Once you've downloaded the plug-in file. Copy it into the plugins folder in your Yoot Tower installation directory. If you're having trouble with the game seeing the new billboard, try deleting the database file in the directory if one exists. This will cause the game to rebuild its cache of plugins. Please note these have only been tested on the English Windows version so far!