A wall panel arrangement is designed for use in retrofitting a wall panel system provided with at least one pair of frame members having inwardly facing flat walls for retaining at least one existing glass panel therebetween. The wall panel arrangement includes an add-on glass wall panel and panel mounting structure configured with at least one receiving strip constructed with a planar body having an outer surface secured to one of the inwardly facing flat walls of the frame members in spaced relationship to the existing glass panel. The body also has an inner surface provided at opposite edges thereof with a pair of flexible resilient wall panel retaining elements extending therefrom and converging towards each other to define spaced apart retainer ends which are frictionally engageable with the opposed faces of the glass wall panel adjacent one of the opposed sidewalls thereof.