Custom L.E.D. Sign???

I want to create my Greek letters alpha omega chi into an led light *the actual symbols*. and i need to know what parts i would need to make a sign that can be programmed to light up in various ways. i plan on using alot of LEDs and i want to program the light from the computer through the rs232 cable. and which program would be best for this what type of chip i should use one thats large enough to store the commands and possibly how to implement a switch on the light itself to dim the lights for night time.