I'm sorry, but we can not answer this question for the general case, because interviewers are not all the same. People who make hiring decisions are all individuals who apply their own personal judgment systems and expect very different things. While one person willmight be impressed by the extra length you went to, another willmight wonder why you are wasting your and their time by adding stuff they never asked for.
What you can try, is to do some research to find out what they are likely looking for:
- Read the job offering description, test instructions and other information provided to applicants very carefully. Read between the lines to find out what kind of person they are looking for. Do they want someone who can follow instructions? Or someone with the initiative to do their own thing?
- Try to find out how they are working internally. Do they have any development blogs describing their development processes? Did people from that company talk about them at conventions like GDCGDC? (by the way, if you do get to the personal interview stage, then showing you did your homework about the company you applied to will almost always earn you a couple extra points)
- Are they a large or a small company? Large companies tend to have very standardized application processes with very formalized rating systems. These simply don't leave room to take any additional work into account, so it's often futile to try to score that way. Smaller companies often tend to look at applications a lot more subjectively and might be impressed by applicants who do things which set them apart from the rest. But this is not a hard rule either.
- Just ask them back whether or not they would want to see supplemental material like that together with your test submission.
If this doesn't give you any pointers, then the best thing you can do is think about what course of action does best represent you and the way you want to work.