Guest Bedroom- style or function?

We have a guestroom, which we haven't done much with. When we moved in, we put in a hand-me-down queen bedroom set. It fit in the room, but it was over powering. It left the room with little function, other than holding guests and some extra clothes.

We want the room to function better for our lifestyle and do some double duty. We aren't exactly sure how to utilize it yet, but we want to start by using a twin bed instead of a queen. It will give us much more room. We pretty much only have one guest at a time anyways.

We are in the process of selling the queen bedroom set on Craigslist. It's my first attempt at Craigslist and it's not going as we hoped. Maybe it's the time of year? Not sure, but hopefully it sells soon. We're hoping whatever we make from that will cover a decent amount of the costs of the new furniture. We only plan to get a daybed, mattress, matress cover, and sheets.

We're struggling with whether we should go for style or function. I'd love to include more pieces that have a design element. Our current pieces are all more traditional and functional.  For style, I'd love something like the West Elm window day bed. I love the graphic design.

Our guestroom is small, so style may not win out. We may need to go with something with more function. I like the idea of having a piece with storage. I'd like something similar to the Pottery Barn Kids Belden bed. I love that the lack of a headboard makes the bed minimal and the storage adds function. Extra drawers are always a plus for us. 

For the next 5 or 6 years, I think style works fine, we don't actually have anything that needs storage in that room, but long term, the storage would be good. Although, things could change in 5 years anyways, so who knows if we'll actually need a bed with extra storage.

What would you do? style or function? Any tips for selling on Craigslist?