Eh, I'd disagree (with Stijn). Sure, saying that tilesets should be 320px is useless, because a) it should be clear from looking at the picture that it's not supposed to be a tile layout (no customizability at all, particularly with the pipes) and b) surely I know how wide tilesets are by now, but it is true that they do not completely mesh, and if this design goes through, that is something that would have to be taken into consideration. Some visual accompaniment to the suggestion is always helpful, but I don't think it's necessary.