Looks like you did not quite get it. Quoting you "It will be much better to delete those files someway".
There are no files. The picture is textencoded within the blockchain. You would have to delete a part of the blockchain to delete the picture.
A friend of mine save an entire image of Windows 7 onto the blockchain. So technically he has a Windows 7 Backup-DVD on the Blockchain for all times.
Oh I see! thanks for explaining it like that!