Was the jpg lower than 1280x1024 and with a size lower that 300 KB? If not, then the picture will never appear.
As you are saying that the week numbers are "along", then I suppose you're talking about the calendar, and not about the week view, so, do more or less the same as you did but instead do this:
Options -> Skins (icon) -> Advanced (button) -> Active skins (list box), Windows, Shadow4-Calendar -> Settings (button) -> unchecked "Show week numbers"
Unless you give us more info, there's nothing we can do.