Some less obvious ones:

• A set of these (or the like). Dining at "work" today? Extra stack of papers? Comes in very handy.
• A window, or one of these. Must-have. Gotta relax the mind.
• A desk lamp. Multiple sources of light, especially around / behind your monitor are very helpful if you're working on a screen all day.
• Bluetooth peripherals. Don't be typing on your laptop, then you're looking at your laptop screen all the time and hunching over. Along with a nice screen, get a decent keyboard and mouse/trackpad/ball/whatever and use your laptop as your secondary monitor.
• Pomodoro timer. Stasis is a challenge for WFHers. Set a timer and get up and move around every 30 mins or so. Do a couple minutes of straightening up, go to the kitchen and fix a drink or snack, take a jog or a walk, call a friend and chat (also very important for WFHers), etc.