If I were in your shoes I'd investigate the tires I really wanted to run.
Then find the tire manufacturers spec sheet for that style and size tire.
On the spec sheet are a few recommended rim widths.
If your rim width matches you now have your answer.
If they call for a different width then adjust your preferred tire size/style or the rim width to suit.

I'm sure there is a general rule as to what rim widths are acceptable for a standard size tire, but I'd defer to the actual tire in question, you can't get a more correct answer than that.

http://www.accuridewheels.com/completeversion.pdf
About page 39 is the kind of general info you're looking for, although that doesn't cover 15" wheels. somewhere there is a version that does..

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-