I prefer a tinplate layout without the traditional green color top. After seeing a couple of tinplate layouts that used a brown, gray or olive top cover as opposed to the "traditional" bright or kellyish green and how those more muted colors made the layout and colors of the respective tinplate trains and accessories seem to "pop" and be the focus of the layout sealed the deal for me.
HandyAndy's olive felt suggestion appears to be a clever and economical method.