ball2.png: 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/share/games/oneisenough/bin/pictures/ball2.png - from package: oneisenough

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

Error in other languages:
ball2.png: bevel nie gevind nie
ball2.png: comandă negăsită
ball2.png: comando não encontrado
ball2.png: commande introuvable
ball2.png: command not found
ball2.png: käsku ei ole
ball2.png: không tìm thấy lệnh
ball2.png: komanda nerasta
ball2.png: Kommando nicht gefunden.
ball2.png: kommandot finns inte
ball2.png: komut yok
ball2.png: nie znaleziono polecenia
ball2.png: níor aimsíodh an t-ordú
ball2.png: no se encontró la orden
ball2.png: no s'ha trobat l'ordre
ball2.png: opdracht niet gevonden
ball2.png: parancs nem található
ball2.png: perintah tidak ditemukan
ball2.png: príkaz nenájdený
ball2.png: příkaz nenalezen
ball2.png: команда не найдена
ball2.png: командата не е открита
ball2.png: 命令找不到
ball2.png: コマンドが見つかりません