System settings crashes when trying to install new icon themes from local file

[Fernando]

Every time, different files. They're supposed to be .tar-gz files, aren't they?

[claydoh]

Yes, most likely.
However, the actual icon files and folders in the tar.gz file may not be set up in a way that the installer knows how to handle. Crashing is bad, though. It ideally would just complain and give an error.
If you extract the contents of the file, you may find instructions on how to install them correctly. User-installed icon themes would ideally be extracted to ~/.local/share/icons, I believe.