Update: As many readers now noticed, as of 10.5.2 there is now a preferences setting for the menubar transparency.
For some reason Apple decided to make the menu bar in Leopard transparent. With my background image this means that the menu bar will be in a shade of blue. It doesn’t look good and makes my computing environment less comfortable (I’m picky, I know…).
Someone created a software hack to remove the transparency. There is also a system setting (thank you Johan) to trick the window manager into thinking it is in older hardware. I am not sure of the side effects so I’m not that keen on installing that. Here is the pragmatic fix: take your background image and paint a white stripe, 21 pixels high, at the top. Problem solved. My menu bar is now easy to read with black text on white background (see picture above).
Before painting the white stripe you may have to resize the picture to the exact size of your desktop, otherwise the OS will resize it and it won’t fit the size of the menu bar.
Update: As Peter points out in the comments below, if you use black instead of white the menu will look similar to the default ash grey style of other Leopard apps.