Why wouldn't you put them both centered on the wall? You don't say what size fireplace you are getting but once you get the firebox installed and stone/tile around it you will probably close to 7 feet for any reasonably sized fireplace. If I did the fireplace on the side with very little tile around it, I would use the other side for a tall shelf and still center the TV above the FP. Personally I don't think putting a TV above a heat source is a good idea, but that probably depends on how much you use the fireplace. If you have the fireplace picked out or any drawings of what you are thinking about, post them here so more people can help you. The more details you can offer the better feedback you will get.

Hire a local designer.

Thank you MSDG I don't know if I'm doing paneling work -- I need help designing the entire wall. The firebox cannot be moved because there is an egress window right next to it on the outside (basement). I'm not looking for the black/white look, I was showing the photo for the mantle style. What do you mean "Furred out portion around fire box?" Do you mean the marble before the wood post section? I can't decide if I should do a heart or not. I like it sometimes, but I need to figure out the entire wall to see what looks good together. I also like the look of a window seat, but I don't want it to look so casual like a kitchen bench. Do you think I should put a new window only on the right side of the fireplace? What are your thoughts on a bench seat underneath it? Thanks so much for your help!!

Here is what we ended up doing. We decided to keep it light and bright and just paint the wall the same color as the room. We can alway tile it in the future if we get tired of it.