I'm afraid the pictures flanking the fireplace are too small to have a positive impact. You could put one over the other on one side and put a larger picture on the other. The middle piece on the mantel doesn't doesn't work for me as a decorative object. A round mirror with a dark wood surround would look better or a genuine oil painting. Prints don't have the same power to draw you in. E-bay has art sold by the artist which is often quite reasonable. Only buy what you love and what has meaning for you. Those are pieces of which you'll never tire, and which can be used in different rooms and homes throughout your life. The Peter Pan figure with the hat is rather whimsical. Only you can decide if it stays, but I rather like it. Three candlestick on the right are all you need, but I would consider something different for the middle.

I rather like the large piece over the fireplace but can't tell exactly what it is. Those are good suggestions to move the small pictures to one side of the fireplace. I know you didn't ask about the children's chairs but do they always sit in that spot?

Try taking everything off the fireplace aside from what looks like the stained glass piece. Then put the two pieces of art, one on top of the other to the right of the stained glass piece. This will create symmetry and will allow you to keep the pieces you truly like.

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I love the stained glass but it's sharing space with too many other things. Remove everything but the glass.

You could keep it off center but add just one other piece possibly round to offset the stained glass.

I agree the two pictures on each side of the mantel are wrong for that place. They mimic the air vents above. Paint the vents the same color as the wall. Might help to hide them a little.

Think of a way to back light the stained glass. The colors would come forward.

Beings the photos represent good memories I would find a way to incorporate them. If you had them placed into frames with a larger mat and did a layered look, like below, they could still be used. I would also, opt for a frame color that contrasts the black mantel instead of matching it.

Lastly, you could accessorize with the candle-holders and small clock you already own , but should balance that out with a tall colorful vase/s on the opposite side. Good luck!

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Ha Ha. Did a mock up before I read what others suggested moving the two pictures to one side. Like that you did. Any one of the mantle arrangements you have works except move the clock to one third of the way to the right, not smack in the middle. Use the other two objects that mean the most to you.

I like the Peter Pan head. It's different and unexpected, which is a good thing.