Manual sprite creation (vertex+triangle+uv). Is it possible?

Is it possible to somehow create a sprite exactly like you create meshes? I got source image with 16x16 tiles, and I need to generate from it 48 different 32x32 tiles, each consisting of 4 tiles from source image. To do so I need to manually set vertexes, tiangles and uvs for sprites.
I found a way to set vertexes and triangles, but there seems to be no way to set uvs.
Is there some workaround for that, maybe using reflection at least?