Well I have my frames made (light timber frame with uv/outdoor rated material on outside) see pic below

Overall dimensions are approx 1200mm x 1000mm x 70mm
I have my 550mm tall seven segment digits and led matrix arrays from scrolling text also (pics to come)
Probably using an ATMEL AVR microcontroller for this project, and due to having a bucket load of spare io, I will probably drive the transistors directly for each segment and multiplexed digit control lines.
Segments have around a 23.5V drop so I am using a 24V power supply for them and I will probably let each segment have approx 100mA, more testing required there though.
More to come!
Dan