I love your Route 66 layout!
What I do to get the images the correct size is open them in microsoft paint, then use the stretch/skew function to reduce the image until it looks like the right size. The size it appears in paint will be the size it shows up as on the message board. I usually start by reducing both horizontal and vertical by 50%, then adjust as needed. Then I save it as a new file.
Hope that helps!
