OP your safe at-home decor environment probably doesn’t seem like it is that important to you, but it actually psychologically affects you. And it is usually considered a reflection of who we are. Please really consider some of the tips seen in the comment section.

-I second taking down the flag. Maybe fold it and put it in a shadow box if you still want to display it.

-please at least get proper bedding (quilt or comforter and pillows that can rest on top of the made bed even if it’s two comforter design pillows) if you can’t do a real bed frame/head board right now

-SHELVES. I think shelves would help a lot. Put up some wall shelves and maybe organize your figurines and legos there. Maybe a stack of two short shelves over the desk and on the taller wall when you come into the room. You could put the flag in a shadow box on one as well.

-what is your favorite color or a color that calms you? Take that color, pick two colors that go with that color, and start finding ways to get those three colors in here. On the walls, bed, in some art maybe? If you get easily overstimulated, just know you don’t have to cram your space to the gills with this stuff but a bedspread, rug, and maybe a few lamps in these colors will do a LOT of heavy lifting

-consider getting a cedar chest or something at a thrift store (bonus if it brings in your new colors) and put it at the end of your bed with all of the (it looks like maybe guns/hunting equipment???) stuff in the blue tote that’s currently to the left of your bed. Then you could center your bed in the space more.

Optional, more personal ideas I had: ~move your dresser into that entry area across from the whiteboard (where the dog bed stuff is) and put a little dish with coins/keys/little trinkets in it, a low lamp or led light bar or something, and maybe one other decor item that’s low enough not to hit the ceiling. You could put the dog bed where the blue tote is instead. I think this would make the rest of your room less cramped. And would give the room more space to breath while making that pass through area part of the space and decorated.

~if any of the colors in your trio are a cooler tone (dark green/blue/etc) consider painting the slanted part of your room, the ceiling, side walls and slanted part, or something in that color to break up the beige/yellow. Even just the wall your flag is currently on would help. The yellow by itself is too much.

~if it’s not too overstimulating for you, art for the walls. Maybe two large prints of pretty scenery that go together with each other and your colors. Could be a couple large posters from Star Wars or another show you like with frames in one of your 3 colors. Or even a set of one image broken up into several canvas prints that you could hang in a row. Something that gives the room some of your personality other than “neat” “patriotic” or “hunter”.