I had 3 boys and what i found worked for them might also work for him. I found boys have mostly no hanging clothes so I put the drawers in the closet to free up space . . Does he like to have sleepovers then IMO bunk beds are awesome . I like shelves on the wall for favorite toys or collections a nice big corkboard for pictures , all kinds of stuff that needs a spot to display. I know people say laptops have all that stuff but I found even my grand kids still used the corkboard. Then you ask him what colors he likes and I will tell you that cahnges often for the next few years.Ao I do neitral walls and use the color of the year for bedding , blinds pillows etc. Easy to change no painting required . Posters of his favorite sport ot whatever .The basket ball hoop probably not ideal in a bedroom you need more space for that. Take him shopping for bedding or go online either works .

My son had bunk beds for quite a while - they are great for sleepovers as Patricia says. When he was a little older than six he liked to sleep on the top bed. Some kids would probably like to be up high like that and others not. When he started getting tall we sold them - I think there's a good secondary market for them if you want to buy used yourself or resell them when he gets older.

Try bed centered on that wall and a trundle is an option for what may be an occasional sleepover, as it won’t overwhelm room visually as a bunk bed might. Add a nightstand on other side and that wall will become a nice feature wall when pictures are added. Try dresser opposite to where it is, so you can add a desk under window or he may prefer a comfy chair.

He's at an age where his needs will change quickly over the next few years, so keep your changes simple.

He's still playing on the floor, so leave as much of the floor space open as possible. The most pleasant place to play is in the brightest area of the room, near the window, so no dresser or bed should be near the window.

Try the bed with the headboard on the longest wall, but not in the middle of the wall. Put it as close as possible to the door, with just leave enough space between the bed and the wall for changing the sheets and making the bed. Add some toy storage under the bed - wide shallow boxes. He's a bit young for sleepovers so use his current bed until you need to change it up and decide between a bunk bed and a trundle - or more simply, use a blow up mattress for occasional young overnight guests.

It looks as if the closet is large, and has bifold doors. That's good because the closet opens completely. Put his current dresser in the closet for now to see how that works out. You may want to change the position of his hanging closet rod to raise it, and add a second rod that hangs below the upper one, beside the dresser. Be sure you're using every square inch of the closet, top and bottom, before adding more furniture into the room. https://www.hgtv.com/design/remodel/interior-remodel/a-boys-closet-for-every-age-pictures

See how that works out for him in terms of using the room before you start buying new furniture. Some cheerful posters would look good on the big wall. I would switch to blackout drapes or blinds that shut out the light for sleeping, and are easy for him to open and close.

Here's the bed placement, and an option. See which works better for his play activities.

I'm wondering where the heating vent is in the room - you need to leave that free of furniture..

Trundles take up too much floor space when 2 kids are playing like a sleep over.

We read to our 6 y/o grandson at bedtime and his room lacks a good chair ( even some kind of fun big beanbag) and light for that when we visit. It’s really hard to squish into the bunk bed, and dark. Have also set up a pillowed wall corner, younger joints handle that ok, but needed a light source ( if not wanting ceiling light on).
So if that’s something you do, think about a reading nook. If no room then that’s that. Would spend a lot of money though since he will outgrow that.

I'd add some color. It might be a big, bright poster. It might be a bright rug. He's going to need a desk soon. It looks like he has a lot of closet. I, also, put my son's dresser in the closet. I put shelves for toys there, too. If you have room in the closet, put as much as you can there and find room for a desk and, if possibly, a comfy chair.

He needs a lamp he can control from bed. I don't know why you have the one lamp where it is now but it's too tall for bedtime use/middle of the night needs. DH built our son a bunk bed early on. They come in sooo handy.

For wall art/decoration, a kid's room is actually pretty easy compared to other rooms in the house IMO. We've picked up pom-pom garlands cheaply from Amazon along with colorful clothespins and use them to hang up our daughter's school projects/art as she brings them home, along with birthday cards or Valentines she receives from friends throughout the year. It's a nice option to avoid damaging the walls, and it's easy to purge/switch out whenever you're ready.

Check out Etsy for removable vinyl wall decals - you can literally get anything depending on what he's into, and they peel off the wall when you're ready to move onto the next phase of style/interests (we're just now removing my daughter's Tetris wall decals, and happy to report they not only stayed put for four years with no bubbling/peeling, but are coming off with zero damage to the walls/paint!).

Also, check out Lego wall tiles - they either affix to the wall or other surfaces like tabletops, etc. and are made to secure Legos for hours of creative play: Brik Tiles

For toy storage, I'm a huge fan of Ikea's Trofast - there are lots of possible combinations and it works great in smaller spaces. The height of the units is kid friendly, and for me, the ability to scoop up toys and stow them away in bins at the end of each day is awesome.

Bunk beds are a preference - depends on how often they'll get used.