As RangerX stated, you cannot do that with GameMaker. The extra color information has to come from somewhere and the blurry / pixelated (depending on the setting) image is essentially the result of the computer's best guess at adding that information.
The only option, as implied above, would be to use vector art. It doesn't add detail, but it maintains detail. Sadly, however, GameMaker cannot render vector art. It can import it but I am rather certain that it converts it to bitmap.
You can start out with a larger image and shrink it, but that just changes the issue from trying to add non-existent information into an issue of trying to subtract the least harmful information. However, this usually does result in more pleasant results to the eye than going the other way around.
Long answer short, if you want nice looking graphics you must design them yourself to be nice looking. You aren't going to be able to do it via programming in any practical fashion.