Nick Stadler designed the tilesets for 320x240. It makes sense in the way that it's his pixel work and with such a small resolution all the work he put in there is more visible. I guess you're coming the same way. However, take note that the rest of the development team didn't have to follow his train of thought - that's why there are bigger resolutions in the game in the first place - and the publishers most definitely didn't, as 320x240 was small even for 1998, when the game was released. And that was 13 years ago. If you prefer, then nobody's stopping you from designing tilesets for 320x240 and playing game that way, but obviously you'll be in the minority, and there's no point in forcing others. Come to think of it, many people would like the game to support even bigger resolutions than 640x480, even though it'd likely break many levels, visually - this including the official ones.