I have an empty room upstairs, i already have a guest room, i was looking for ideas from ya'll what do you thi?

It depends upon your interests. It could be a game room, a library, a really cool place for mediation or yoga or a spiritual place that is calming. It could be a work station for computers and office stuff. A craft room where you can work on a new hobby like stained gl, quilting or ceramics. You could turn it into a garden center and have plants and plant lights. It could be a Christmas room with a tree and all kinds of Christmas stuff that you can keep all year round! So, it is totally up to you and your interests.