What can I do with wood paneled walls w/ fireplace of grayish brick?

You can paint it using a good primer first, or do a whitewash on it, which is just watering down the paint to get more of a rustic look where a bit of the paneling shows through. Or, you can fill in the gaps between the paneling to make it look like a regular flat wall when you paint it. Here are links on all of these:

https://www.todayshomeowner.com/video/how-to-fill-grooves-in-paneling-before-painting/

https://www.laurengreutman.com/paint-over-wood-paneling/

https://annieselke.com/its-a-wash

i would paint it.use kilz first then a satin primer paint color of your choice.maybe a favorite color in a pillow or throw to tie it all together...

Oh my dear friend.......paint it! Clean the walls with warm water and TSP. Fill all holes with spackle. Prime with Kilz2 (apply several coats if you are going with a light color of paint.) Paint the walls with interior paint in a satin finish. Two nice grays: Glacial Stream #HGSW1477 and Icy Avalanche #HGSW1497 by Sherwin Williams are two pleasant choices. Both colors will complement your fireplace and will definitely lighten up the room. Also, start with the ceiling. Repaint it with a bright white wall paint (not ceiling paint) also in a satin finish. You'll be surprised how large your room will feel when done. Best of luck.

We painted the paneled walls in our entire home and love it. We also painted the brick fireplace, but you can do the same with stone. What a difference it will make in your home - like it did with mine! Here is an example of what the stone can look like - not my photo:

I agree totally paint the walls and while I are at it paint the fireplace a shade darker than wall paint. It will give your room a much needed face lift. Alternativel, if your are into tonthe whole ship lap thing ala Joanna Gaine, might ship lap the areas beside the fireplace and paint.

We just painted our paneled living room this past Summer. What a difference!!! Totally brightened it up! It took 3 gallons of a very good paint\primer. I did not use Kilz. The paint/primers are really good now. Also, we did remove all the old woodwork and afterwards put up all new trim. I painted a light cream color. It did take two coats. The verticle seams were all brush painted and thoroughly dried. I also filled in every nail hole before I painted. Then after I was happy with the brushed seams, I rolled the entire room. It took two weeks to get it done, because of work. I used a satin paint. I highly recommend not using a glossy paint. I know someone who did and the room has a hollow sound. Satin is perfect for a living room. Well, I hope this helps!

Paint the paneling! It will look awwwwwesome! Leave the seems.... kils first👍🏼

I agree with skipping the filling of seams. Paint it but you can also have an accent wall with planking done with 1x4s and stain. Or do the whole room with horizontal planking. This is what we did in one of our rooms that had paneling. Not finished yet. It is kinda of dark in the room no light but from the closet. Replacing fixture but used several stain colors.

I painted my disabled neighbors for her as she hated how dark it was in there.... we had a couple gallons of left over white semi-gloss kitchen and bath paint which I added 1/2 c of baking soda to it to make it look like chalk paint. Came out fabulous and so much brighter. I washed walls with car sponge and ammonia water. Then cut in the grooves with the paint. And then just painted 2 coats as she didn't want to buy primer.