I know that there are a lot of threads referring to that issue, but my problem is different.
I'm running Debian testing. I totally removed gnome-shell and turned it to xfce4 following the official wiki here: Install Xfce in an already installed system
From the first loggin i realized that some application (i think mainly those that where launched as root [like synaptic] but not only them) were looking ugly, not even sing the default theme.
I followed some instructions and I found that I had to install the themes to /usr/share/themes and the new icons to /usr/share/icons. I did it. Nothing happened. Then someone else said that he fixed his problem by installing lxappearance and runninig it as root.
I did it, and thigs gonne worse!
Now, nore applications look ugly (for example gnote) and no only that, but tollbar icons have been removed as well. Look the keys in the gnote toolbar in the photo.
I thing something went wrong with the permissions. Any ideas?
Which theme are you using? Does it have any engine dependencies? This can break a theme leading to a Widows 95 look.
It happens with any theme, even those preinstalled. All gtk2 and gtk3 engines are installed!
In Debian Stable I have gtk2-engines and gtk2-engines-xfce.
Have you selected Style in both Settings > Appearance and Settings > Window Manager?
Do themes work OK in ~/.themes?
Try launching an application in a Terminal and see what theme-related error messages it throws up.