When you're looking at upgrades to your home, they're not all created equally. In fact, if you're looking to recoup your investment when the time comes to sell, there are some upgrades you should avoid completely and some ideas from which you should steer clear.
First, avoid pools. Swimming pools in general are often viewed by prospective buyers often as more of a burden then a benefit.
And looking more broadly, any update that is intensely personalized (a dark room for example) probably won't be perceived as a positive selling point.
For more bad upgrades, head here.