Some very good advice above. Nevertheless, it is also well to remember that all woods are living.It may sound strange but all woods move to some extent with the change of temperature and humidity - which is the reason why hard woods with tight grain are preferred in decorative cabinet making and the like. I would avoid all forms of ply if the board is to be used over long periods, but agree it would make a satisfactory improvised panel.
Even famous artist of old came unstuck by not selecting the correct woods with little movement for their art work. I would go for ebony personally. Good luck Stan. L-B