I’m assuming that you’re talking about the Halo H-1499 low voltage housing with the 1420 slot aperture trim. These slot aperture trims are geared to get the light centered on the wall at a maximum of a 45-degree angle. You can try a linear spread lens that can help spread the light either vertically or horizontally. There is also a diffusion filter that looks like frosted glass, which can spread the light more evenly both horizontally and vertically. The third option is to go to a different trim that has a scoop that will allow up to a 90-degree adjustment (like the Halo 1997 trim). Or you could just hang the art lower and call it a day.