Funny coincidence as I just read the other post on covering bricks.

I have a stove fireplace with legs that sits on a bricked slab along with the mantle being brick. It's in dark ordinary looking bricks and is looking a bit old fashioned now. I was wondering if I could do anything to cover over the bricks, rather than trying to pull it all apart?

I looked at the link for Eldorado Stone and am wondering if there are other products, like slate or marble?

Can bricks be bleached or the colour of mortar somehow changed?

Sorry, but you can't bleach brick, the color is fired into the brick and its forever. You can stain and/or paint. Slate, tile or marble can be applied but you would likely need to first install a backer board to insure everything is perfectly flat. You can apply Eldorado stone directly to the old brick because they are very irregualr. Tile and marble like to lay perfectly smooth.