24×24 LED display is formed using nine 8×8 Dot LED matrix displays connected to AT90S2313 MCU. MCU scans an indicator line in series. A special PC program is written to draw images on the screen and transfer them via a COM port to the device. You can send pictures in series that gives an animation effect.
The circuit is built using obsolete AT90S2313 MCU which can be replaced by Attiny2313 MCU with minor modifications of the firmware.
Your event doesn’t need to connect the device to the computer COM port to make the program work. You can store images in other master MCU EEPROM memory. Each received byte from UART is immediately sent to 8 LEDs, the second byte to the next 8 LEDs, and so on. Bytes have to be addressed one by one without delay. USART is working at 115200 baud, 8bits, no parity.