I'm looking to create a simple circuit that will have 8 randomized "pulsing/fading" LED's
The CD4026 has a Display Enable pin that you can apply PWM to. The question is, how to make the PWM vary in time with the LEDs? One possibility is to use the triangle waveform that the NE555 is already producing as it clocks the CD4026. 

In the circuit below, OA1 and OA2 form a classic Pulse Width Modulator. OA1 generates a high frequency triangle wave on C2. OA2 then compares this to the much slower ramp produced by the NE555, and outputs a PWM waveform with varying duty cycle. This should cause the brightness of each lit LED to go from 0 to 100% and back again during its time segment.







simulate this circuit &ndash; Schematic created using CircuitLab

If you want the LEDs to fade in and out at a different speed to the randomizer then use another 555 (or another opamp) to generate the brightness ramp. If you want the brightness of every LED to vary independently and/or randomly then you will need an even more complex circuit, in which case it might be easier to program an MCU to do the job.