1. Replace the slim mantel with a heavier one.
2. Remove the oak and replace it with matching brick, if you can find some.
3. Remove the oak and replace it with a mirror.
4. Paint the brick white or another light color which works with your house decor.

I would remove the oak and replace it with cement tiles or I would put cement tiles on top of the oak. Then I would add a piece of artwork.

The possibilities are endless as long as the purse is deep ;-)

Is the wood panel embedded within the brick or attached to the face of the brick? You could cover the whole upper part with drywall and molding. Find a pattern/design you like, of course.

Or reclaimed wood?

thanks for the ideas. Kim, to answer your question, the panel is embedded. not sure what's underneath!

Someone suggested covering the panel with a custom wood art piece. and I've incorporated some other suggestions as well. thoughts?

What is the purpose of the wood panel? Is it attached to the brick or directly to the drywall? I'm usually in favor of removing over covering up so I would take it down. If there is brick behind, you can either leave it or address all the brick. If there is drywall, then you have a brick frame for whatever you want to hang inside (or set on the mantel). It gives an interesting opportunity for something sculptural/three dimensional.

You could cover it as you said with a custom piece as long as it will sit flush. You would have to take into account the sloped angle at the ceiling. Not sure I would match it to the wall color, since that is something you might change at some point in the future.

Honestly, I would cover all the brick above the mantel with dry wall and hang a large piece of artwork on it. And as suggested previously, you could get a more substantial mantel and hang it lower.

Lower the mantel, then remove everything above it. A flat wall with art will make a big difference.