My bedroom is booooring! We are by the beach so I used grey, brown and white to get a beach cottage feel even though we are in Costa Rica. But I have run out of ideas and the room looks pretty bare and boring.
I also vote for cream. I had a red living room back in the day and I found cream really let the colors pop. Also b/c your art work is floral and light in color I think going too dark will make the elements of the room seem disjointed.
I like the look of items above the fireplace as opposed to across particularly in small places. By drawing the eye you make the ceiling seem taller and by extension the room seems bigger. I think in a shotgun style living room that might help.
I would make a collage using copies of the pics. Back it on a thin plywood and you can even add a frame, if you would like. Then put it on the mantle and group the dinos on each side.
Finally, I'd fill the shelves on the side of the fireplace with larger or taller items that fully fill the space provided without making it look too cluttered. Empty shelves make it seem like you didn't finish. I would separate the red vases on the bottom left putting them on the top right and left shelves so they mirror one another. The shelf with the red and black block painting with the yellow clock piece looks wonderful. You could move that to the top and then put the red vases on the center shelves. But the idea is to have some mirroring so it all comes together.
I think you need to add a little height to the both ends of the credenza.
I would start with the side that has the clear round vase. I would add a taller vase to fill the space on the wall. I think a bold color would tie it in with the lovely picture you have framed. You might also group a few small things around the vase. Perhaps, the owl and the pictures.
Then on the other side keep the taller dark picture frame and group the remaining items. This should leave some space in the center. Here I would put a tray and add the teacup plant with smaller picture frames or knick-knacks on either side.
Finally, store the watering can elsewhere since it doesn't go with the other lovely items you have.