fbsetbg: 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 CentOS possible default full paths are:

/usr/bin/fbsetbg - from package: fluxbox

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/fbsetbg - from package: fluxbox

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

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