I want to change an icon of a specific theme. Where do themes save their icons?
or in your home folder :
/usr/share/icons/ typically contains pre-installed themes (shared by all users)
~/.icons/ typically contains folders with the themes installed by the user.
Also, many applications have their icons in
/usr/share/pixmaps/ or in the folder with the same name as the application under
There are several places: (in bracets some examples)
/usr/share/pixmaps/( chromium-browser.png display-im6.q16.xpm firefox.png flash-player-properties.png gimp.xpm gvim.svg texstudio.xpm )
/usr/share/app-install/icons/( adobeflashplugin.png julia.svg texmaker.png thunderbird.png vim.svg vlc.png wine.svg grace.svg)
~/.local/share/icons/( soffice.png java-lang-thread.png org-jabref-jabrefmain.png) one of the places where Ubuntu searches for icons, if you use relative path
/usr/share/icons/...and subfolders ( matlab.png .../hicolor/scalable/apps/chromium-browser.svg .../hicolor/scalable/apps/geany.svg .../hicolor/scalable/apps/okular.svgz .../default.kde4/48x48/apps/acroread.png)
/usr/share/...just subfolders ( .../vlc/vlc.ico .../gimp/2.0/images/gimp-logo.png ) but this one is more for icons used in the program that the logo of the program
/snap/...just subfolders ( .../inkscape/3080/meta/gui/inkscape.svg .../languagetool/10/snap/gui/icon.png )
~/.iconsunlikely, that folder exists (but sometimes )
Most of the folders are already announced here, all sources I used:
As a supplementary for the accepted answer: If you don't find the
~/.local/icons directory, there may be a
~/.local/share/icons directory instead (PS: My distro is Ubuntu 16.10).