I installed an Icon theme with elementary tweaks, I guess it was broken because the settings force closed, wingpanel disappeared and most of my apps won't start anymore... Right now I can only open firefox and the terminal... Is there a way to either delete the broken icons folder, or change the icon theme through the terminal?
Good thing Terminal still works :) Open it and paste the line
gsettings set org.gnome.desktop.interface icon-theme 'elementary'
The default icon theme should now be restored.
The reset to defaults is in the about menu in Administration.