If you haven't already, even though you just upgraded, I would to a
sudo apt update && sudo apt upgrade
Then assuming that all goes well, a reboot. Sometimes even just a log out and in will fix icon issues (especially in gnome) but I just prefer the slow and steady reboot.
When you say "icons on the screen" do you mean the desktop, or also under the main menu? Can you also take a screenshot of what you see when you try to launch something?