gifbg: 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/gifbg - from package: giflib-utils

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

On Debian possible default full paths are:

/usr/bin/gifbg - from package: giflib-tools

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

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