Re: missing icons
I had a similar problem to that you describe, with some launcher Icons showing & others not; placing the cursor over a missing one, showed its name, but nothing worked when clicked.
That may not be exactly your problem, but I cured mine with:
sudo apt-get install --reinstall ubuntu-desktop
"Better Solutions may bring Worsened Problems": After Lao Tse, b. circa 405BC. a contemporary of Confucius, who died circa 600BC.
They did things differently in those days, apparently!!