Display flicker

Does it do this all the time, or say only after Sleeping?

Couple of things to try if you haven't...

Have you done a PRAM reset, CMD+Option+p+r...

http://support.apple.com/kb/ht1379

In fact, do 3 in a row, takes a bit of time.

Intel-based Macs: Resetting the System Management Controller (SMC)...

http://support.apple.com/kb/HT3964

(SMC reset= Shut down, disconnect power cord for 10 seconds, reconnect power cord, wait 5 more seconds, turn computer back on)

but it is slightly different: (PMU REST = Shut computer down, disconnect power cord for 10+ seconds, reconnect power cord WHILE SIMULTANEOOUSLY PRESSING POWER BUTTON, let off power button for a few seconds, then press power button again to restart the mac mini.)

Good work! 🙂

I think the screen & new LED lights are flickering at slightly different rates...

Refresh Rate and Room Brightness

LCD screens are always flickering during use, but the human eye doesn't see fast enough to notice the flickering if the screen updates fast enough. LCD TVs are much less prone to having screen flicker issues than older Cathode Ray Tube, or CRT, screens because LCDs have a higher refresh or update rate, and light the screen more consistently. However, if you're viewing an LCD under a very bright or very dark lighting condition, you may notice your LCD TV's normal screen flicker. Adjusting the screen or room brightness can resolve this type of issue.

http://everydaylife.globalpost.com/possible-causes-flickering-lcd-tv-screen-3586 6.html