gtk-chtheme: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/gtk-chtheme - from package: gtk-chtheme

You may install the required package with command apt-get install {package}

Error in other languages:
gtk-chtheme: bevel nie gevind nie
gtk-chtheme: comandă negăsită
gtk-chtheme: comando não encontrado
gtk-chtheme: commande introuvable
gtk-chtheme: command not found
gtk-chtheme: käsku ei ole
gtk-chtheme: không tìm thấy lệnh
gtk-chtheme: komanda nerasta
gtk-chtheme: Kommando nicht gefunden.
gtk-chtheme: kommandot finns inte
gtk-chtheme: komut yok
gtk-chtheme: nie znaleziono polecenia
gtk-chtheme: níor aimsíodh an t-ordú
gtk-chtheme: no se encontró la orden
gtk-chtheme: no s'ha trobat l'ordre
gtk-chtheme: opdracht niet gevonden
gtk-chtheme: parancs nem található
gtk-chtheme: perintah tidak ditemukan
gtk-chtheme: príkaz nenájdený
gtk-chtheme: příkaz nenalezen
gtk-chtheme: команда не найдена
gtk-chtheme: командата не е открита
gtk-chtheme: 命令找不到
gtk-chtheme: コマンドが見つかりません