If space is tight, is there a reason why you want a queen-sized bed? Unless your visitors tend to be couples, I would use a twin bed, or perhaps a day bed. If there are couples visiting, a full bed should be adequate. Alternatively, a sofa bed may make the most sense since that can be made a full bed and allow other uses for the room.

I would keep the walls neutral - a nice soft white will keep the room looking larger. Concentrate on color splashes with the accents - Table light, linens/spread-comforter-pillows for bed, some art on the walls. It can come together quickly. You didn't indicate colors you love or hate, so not sure what pics to give you. But I feel confident that you keeping the pallette neutral with the walls is a great beginning.

Thanks for the feedback! I tend to stay neutral but add splashes of color on walls, linens, art. Since it is a guest room, I thought I would branch out with the paint - staying away from pastels. I like richer colors but could like a greyish blue.

You could do beige without being boring. Add a touch of animal print. Really cool lamps and art and luxurious bedding. Sparkle works too for interest. Texture, sparkle, pattern in a monochromatic space looks great.