I would get a vent deflector(see pic) and put bed under window. Consider painting that wall a deep color. Mount swing arm lamps on either side. Move dresser to wall where bed was-centered if possible. Add a mirror above. I would make a Roman shade for window. Pinterest can tell you how. I would do in a colorful jewel toned fabric. I would get a little snack table on wheels(see pic). For drink, laptop, writing a note. Nice piece of artwork on wall opposite dresser. And if it would fit, an ottoman on wheels.

I like the daybed as it is. Just add one round pillow in center. Otherwise, you have to take all the pillows off when you open the bed and they all end up on the floor!

You could also add a small lamp on dresser.

Always fun to have a challenge to make an attractive guest room on a limited budget. I'd step back and consider how you can use the colorful rooms in your ideabook for inspiration instead of going too dark. Look around your house or Target or Walmart or World Market for a colorful inspiration piece, perhaps a new rug, a table lamp, or cloth runner for the top of the dresser. Add white bedding and two bed pillows per person. Add a map of the world spray glued to a bulletin board (like in your ideabook) with some bright pins to indicate where previous guests are from (and a note to invite current guests to add their own pins). For curtains, buy simple white panel curtains with blackout liner from amazon- you can't make anything cheaper yourself. The lamps can be spraypainted white or red to freshen up the worn out brass finish. Put them on the wall next to the bed at locations where you can turn them out from the bed. The rug could be replaced with something more cheerful, larger, welcoming, and homelike (and washable).

Very important: add two luggage racks with backs to protect the walls, a lightweight easy to move chair, and two electrical power strips. If you supply a couple of electrical converters, your international guests will be profoundly grateful that they can plug in their computers and recharge their phones without bothering you, their host.

Here's a white and bright guest room:

And here is a whimsical hedgehog lamp: http://www.target.com/p/hedgehog-figural-table-lamp/-/A-15933278#prodSlot=_1_20

Leave the day bed as is. Can you center on wall and still have space for a nightstand/small table? Rug does not need to be underneath day bed. Pull it out and center in room. I like the idea of a more fitted cover for day bed. Get some fun colors in with your pillows. Maybe paint the dresser.