I dont think you're gonna get a really metallic effect without making some new tiles, though. Octorock is right, the Level 1 Pallette from Orion's old tileset has the right colors... but it just doesnt look metallic cause of the tiles involved. I'm actually looking at making a metallic level myself, and Ive found the best games to rip from to make it are Mega Man 7 (if you want a technological level), as the sprites are big, colorful, and easy to rip/recolor. If you want more subtle tiles, try the last level of Secret of Evermore.

-C