This is a child's bedroom.
Because the room is small, around 12x12,
without a closet

When we built our house a couple of years ago, we wanted to maximize the
space in the two smaller (12x14) bedrooms by not building in closets.

One of the rooms is my home office, so I have a bookshelf, my desk and a
bank of wall cabinets over the desk to store additional supplies. We also
have a piano and a treadmill in the same room with plenty of room to spare.

The other bedroom is my daughters room, and I built a pair of armoires to
sit on each side of her window. The one on the left holds her games, toy's,
and other similar items. I have a divider in the one on the right, giving a
rod to hang long clothes, and two rods to hold shorter clothes. In the area
between the two armoires I built a window seat with four drawers underneath
to store socks, underwear, and that sort of thing. She even displays her
dolls and stuffed animals on top of the armoires. This gives her much more
storage than a closet and dresser would have, and takes up very little
space in the room. They're basically just cabinets, and any cabinetmaker
should be able to build armoires to fit the space. I would recommend doing
as we did and make the shelves, closet rods, and center divider removable.
You never know what you'll want to do with the room in the future. Once my
daughter moves out, I can take out the closet rods on that side and install
more shelves. It'll probably become my wife's craft room.

Since your room is a childs room, you might want to consider drawers and/or
cabinets UNDER the bed. Beds take up most of the space in a room, so why
not make use of that space. Depending on how high you make the bed, you
could store a lot in that area. I've seen ready to assemble systems that
include small closets and even a desk under the bed.

You also might want to search around for "dorm ideas". College dorms are
usually very small and people have come up with lots of creative ways to
make the most of the limited space.

Anthony