On my TUXEDO InfinityBook Pro 15 v4 running leap 15.0 with KDE Version 5.15.5, I made some changes and try with the icons using systemsettings>icons and changing some icons of some applications, but after this when I gone back to oxygen icons the systemsettings icon isn’t the usual but a sort of white sheet, how can I go back to the original and reset all the icons to the default oxygen?
If a logout re-login to KDE doesn’t restore the correct icons then delete the icon cache “~/.cache/icon-cache.kcache”
it doesn’t works, after reboot the system settings icon remain the sort of sheet:|
OK … strange, normally removing the icon cache cures such problems.
What does the (KDE) Menu Editor show as the icon associated with “systemsettings5”
If that’s shown correctly try removing the rest of the KDE/plasma/qt cache files:
~/.cache/ksycoca5_*
~/.cache/qt_compose_cache_*
~/.cache/plasma-svgelements-*
~/.cache/plasma_theme_*
The ‘sheet’ means the icon file is not found in the current icon theme. The .desktop files for the apps store the icon’s name if you change it, but not the path to the theme. Changes you make apply to the current theme. At least, that is the logic I see in what is described. It would mean you’d have to re-apply your changes.
Maaanythanks knur 
I found that in myhome/.local/share/applications there was a systemsettings.desktop file different from the one that was in usr/share/applications, so I deleted the .local one and everything returned as I will.
the correct hammer and wrenc icon is shown
I deleted all the cache files but it didn’t worked