I think the first thing you need to do, to make things at least "appear" uncluttered, is remove 80% of what you have on the walls.

There is just too much going on. Tons of small items makes it look like you are trying to show off every piece you have.

Agree, need to edit. This would be a nice room with a kind of cottage vibe. Lighter furnishing and curtains. Look for a few furniture pieces that do double duty like a credenza that can store file folders as well as dish storage.

As it is spring soon. A good bit of spring cleaning is in order. Take everything out the room. Put in only the essentials so you have good bones. Then like a lady accessorizing add lamps and rugs that coordinate. Finally like jewelry use a few great pieces than a whole load. If they are sentimental you can rotate them over time.

If you would post a few more pictures from different angles in the room, you would get more helpful comments. I wonder if there is room to install a wall of bookshelves that could more handsomely display your collection of keepsakes rather than trying to display on the wall as art.