Are you currently living here, just moving in or putting it on the market? As for your specific questions; look into getting a new mantel, much thicker and interesting, that can be slipped right over the current one. If you find the brick too dark, consider doing a whitewash or a German Smear technique on it. Heat proof black paint can freshen up the metal parts of the heatilator. What material is the wainscot? Is that just paint below or some kind of wood or product? Paint might be the key to that issue. A round table would work well in the squarish room. I'd look for more of a farmhouse style chandelier. If you're just moving in, I would wait on anything major in the kitchen. For now, just remove the wallpaper and paint it. Light sage green will look good with the pine cabinets. I can't tell much about the rad, but a table built in right over it might work if the height is correct. Look for radiator cover under Photos here at Houzz for ideas. You might replace it with a lower style one and then build a bench over it. Rad bench German Smear on brick

I need help with what to add to my mantle that will go with my bull! I have a few things to the left but I don’t care for it. Any suggestions?

IMO a large piece of art would be a lot better choice on that wall and be careful with mirrors they need to reflect something you want to see twice. If glam is sort of the style you are going toward something like these for art work ideally with some other color to use for accent and IMO the recliner really needs to be somwher else and be replaced with a nice chair and ottoman maybe in a pale blue leather

What kind of TV: 1080p or 4K ultra? The distance you should sit from them for optimal viewing ranges from 7.1' to 17.7'. Once you've made that determination, I would consider turning the sectional so that the corner seat aligns with the vent on your wall, but the whole sofa may be pulled out quite a way from the wall, depending on the TV type and your measurements. Angle the lounge chair left of the fireplace by the window. Then with the vent and a gallery, paint the vent black or another main color from the art you will be using, and frame it in a frame that is similar to your other framed pieces. Make it appear as a piece of art. Center the entire gallery 5' above the floor and make sure the vent is surrounded by other pieces so it doesn't stick out. You can cover a great part of the wall if you have enough art to do so. Keeping the arrangement random will help the vent to disappear into the gallery. To fill the rest of the area, I would put a very large ficus in front of the window right of the fireplace. Here's an illustration. See the horizontal piece in a black frame just above the blue and white piece over the sofa. That would be your vent; painted and perhaps with a faux mat painted around it and then the frame around it. The more mixed your subject matter is, the less likely that the vent will stick out so much.