I did change the number oft LEDs. I think I will use even more than 140. I do now think I will use 192 LEDs arranged in a 24x8 matrix. The LED-PCB could than look like this:

This would still fit including a control PCB of the same size inside 5cm x 5cm. I do also have some first idea about this control PCB. I did found two LED drivers witch I could imagine to use for that:

• 24 channel LED sink driver controlled by built in 24 Bit shift register. With this I would power the columns. The row would be multiplexed and driven by discrete transistors. Possible parts:
  • STP24DP05BTR
  • TLC5947
  • MBI5368
• Two 16 channel LED driver (8 outputs unused) . Similar as above but maybe cheaper possible parts:
  • MBI5026
  • TLC5928 / TLC59282 / TLC5926
  • MAX6971
  • STP16C596
  • A6279
• Three 8 channel driver similar as above
  
  • MBI5168 ... MBI5171
  • CAT4008
  • TLC5916/7
  • AS1109
• HT1632C: all in one driver for big LED matrix. Controlled by SPI interface.

Additional to the LED driver I would also include an microcontroller.Although this would be optional if using the HT1632C. But so you can implement stand alone applications and different interfaces (uart, i2c, parallel). Depending on the LED driver and interfaces (== the number of needed IOs / peripherals) I will probably use an ATmega 8a, 328p, 16 or 32.