Resolution doesn’t matter too much anymore since most boards are now done digitally. Of course, they shouldn’t be too low that they can’t be printed clearly at about post-it note size for a portfolio or photostat (this is the entire board printed and scribbled on for notes or other purposes). Generally the resolutions seem to be 150 or 200dpi, depending on the might of your computer (we used 150 at Disney, Dreamworks uses 200 but it can lag quite a bit). I uploaded a 150dpi here, but it can be increased as seen fit. For cinemascope, it’s 1500x638px at 150dpi or 2000x851px at 200dpi.