The network of LEDs D9-D20 remains unchanged. Just modify each 555 to look like this...

Of course, the LED color is up to you. You can also use one fixed resistor instead of the variable. You can buy Darlington transistors prepackaged, no need to use 2 transistors unless they are in the junk box.

Ive got some 4017's, would I be able to add those to this for any additional effect or control?

 

this is going to get built tomorrow after work,, stay tuned for assistance..lol... and this will do 20 leds without further modification? what does the variable resistor do, control speed?

It could do more LEDs, since the load of D1-D8 should have been removed and put onto the emitter driver transistors.

The pot is indeed just a flash rate adjust.

and pin 3 of the 555 still goes out to the network?

Yes, pin 3 is the output of the 555, and will drive the remaining qty 12 LEDs (D9-D20)

I could think of some things to do with a 4017, but not off the top of my head.

 

I just picked up a few earlier at the esco, and Ive seen them in other LED arrangements so I figured they might have a purpose for me...