Depends on your needs.
A good use is to take in exchange students.
turn it into a weight room
A gym
be creative I'm having the same problem and now that i think about it, you could turn it into a toy room or a computer room, just think you may not be able to turn it into a gym or a rocket, but you can turn it into something useful!
Can you please switch on the bedroom light?
To turn on the bedroom lights, locate the light switch on the wall near the entrance of the room. Flip the switch upwards to turn the lights on.
Yes, I have put my shrine (table with flowers, candles and Buddha statue) into my spare bedroom and made it my meditation room.
Your Servant will not work for you until you pay them. They will not leave without warning unless you remove the spare bedroom. If you do remove the spare bedroom, a message will say that your servant has temporarily left and will only return when another spare bedroom has been made. The servant will still be there if you don't pay them but they will not work for you.
Paint the walls
A Guest Room is a spare bedroom in your house where people sleep when they are visiting you.
allow it to sleep peacefully in the spare bedroom
To turn on the bedroom light, locate the light switch on the wall near the door and flip it up to the "on" position.
If you don't want a guest bedroom for your house, you can always turn that room into a home office or a library. Another idea would be to turn it into a multi-purpose room or a hobby room.