With bookcases on either side of the fireplace, the firebox opening will be recessed next to the bookcases. I would check out websites, home decorator magazines, and whatever other sources you might think of to find out what that will look like, and whether it will please you. You might want to consider installing some kind of frame or mantle around the firebox to give it visual importance so it will "stand up" to the bookcases.

The other consideration is one of safety. With brick surrounding the firebox all around and a brick hearth, you have plenty of noncombustible buffer. But make sure that your bookcases start some distance from the edge of the firebox, or they may pose a fire hazard. That distance, sometimes called "clearance", will vary with the particular fireplace. Prefabs usually come with an owner's manual that specifies the clearances. In your case, you might want to get a certified chimney sweep's opinion.

For your questions about color scheme, you might want to post a query on the decorator forum.

You might look at travertine tiles as those would be in your color palette or even some granite tiles. If you go travertine pick tiles that don't have a lot of fill holes as these might open up due to the expansion and contraction from the heat, granite is an excellent choice if you find one you like. As far as the required clearance goes, you should check your local building code as it varies from jurisdiction to jurisdiction.