Yes, most definitely stick with your new tiles. Everything is looking pretty good right now, but a few things jumped out at me. The first is where the water meets the ceiling of the submerged cave. I think that if you just take the brightest highlight off of the rocks they would look better because, right now, it looks as though the water falls a few feet and goes around the dry ground. Also, the pillars aren't very clear right now, so it took me a little bit to figure out exactly what they were. Maybe just a little more definition around them would help with this.
Other than those things you're going a great job working with the EGA palette. The tiles are very well made, and I would definitely play a game with these graphics.