While the tank is a good size, in terms of volume, the lateral swimming room needed by large active fish is still lacking. I would definitely not consider a naso or other large open water tang. Go with a smaller zebrasoma sp. (yellow, scopas, purple), or even a kole. You could likely do two of these if you plan it out. Given the tank height, shoot for species that will inhabit all areas of the water column. A small shoal of chromis for the middle/top. A bottom dwelling goby, a dwarf angel. If it's to be a FOWLR, one of the hardier butterflies would be nice. You have lots of choices, but know the tanks limitations. People hear "144 gallons" and figure the tank to be enormous. THe odd shape is restrictive however, so stock accordingly.