xscreensaver-getimage: 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/xscreensaver-getimage - from package: xscreensaver-base

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

On Debian possible default full paths are:

/usr/bin/xscreensaver-getimage - from package: xscreensaver-data

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

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