After the upgrade my Mac booted as normal and everything was usual until I got a freeze and the following situation in my screen.
I restarted my Mac and it was back to normal until it happened again. I also thoroughly cleaned the inside of my Mac(including the RAM ports) so that no dust is in the way of the circuitry.
A quick Apple hardware test returned no problems as well. At night, I left it alone to make a thorough test but when I woke up, it was long finished and booted automatically into OS X. So I couldn't see those results.
I also reseted my NVRAM, SCM and used Disk Utility to fix the permissions and check the hard-drive state.
Therefore I replaced it back with the old modules that came with my Mac.
I'm thinking of bad RAM modules. When it goes to that block it crashes. I already started the return process for the new RAMs I purchased but wanted to get a second opinion. The broken pixels with the ripples are related with the RAM modules, right?