I still suggest flat white paint, but, if ya want to be a little more fastidious, check out the white 'tileboard', at Home Depot ... it's cheap (about $8-$9, for a 4'x8' sheet), and should last a lifetime ... I took a light meter with me to HD, and compared it to other white, and reflective surfaces there ... the tile board reflected the best :thumbsup: ... totally waterproof, it's made for damp areas, like laundry rooms, shower walls, countertops, etc. ... it's 1/8" thick formica, with one side glazed with a white, porcelain-like coating ... it's also what they make those 'dry-erase' marker boards with, sometimes ...
check out the 'tileboard', I think you'll like it, too :thumbsup: