Wainscott back, recessed center panel
Rustic wood, with simple posts
Wainscot panel, recessed center. Could also be raised center panels
Picture frame molding example
Could use flat molding and create this look on back of island
Plain back with decorative corbels.Could box in the ends of high bar like this is showing
Raised panel wainscot back
Picture frame molding - fill in boxes with the painted material of island? Just a thought
Use wide "columns" to create dimension on back. Could keep panels between columns or just leave flat
Place simple corbels on wide "columns" affixed to plywood back
For laundry room- do you like corbels supporting upper cabinets?
Add doors to top and use cabinets below seat.
corbels, molding in center