If it is a twin bed length ways against the wall like a sofa you can by a day bed set that is a standard twin and have a attached skirt and have that tucked look. I thinking tucking is a hassle day to day. lol

Is your child really messy? Sounds like you need something that wipes clean, if they are. SO no fabric options. But remember that they wont be young for very long, and you will have the bed for many more years. I say go with ewhat you like most and scotchguard it. Also, what is high gloss?

Please post photos of the space as you will get better help.

Yes you definitely need a large painting/print on the wall behind the bed. Even wallpaper would look good, if that is your preference. window treatments will soften the room. a large floor rug positioned half under the bed, and wide enough for feet to be on when getting out of the bed. This will add warmth and texture. The polished concrete in the bedroom makes the room appear cold and not inviting. Add texture with light coloured Manchester, and cushions, And Throw rugs. Light wooden side tables, with side lamps. An upholsterd chair in the corner.