Back in the day when I was working at the University of Wisconsin Cartographic Lab we created graphic design guides with different size type, lines, and area shading. Such guides provide, for example, a quick idea of what 10 point black type over a 50% gray background looks like, and help to see design alternatives.
I include a simple monochrome graphic design guide in the Making Maps book in chapter 7, on intellectual and visual hierarchies (excerpt). Three downloadable versions of that guide are available below (in Illustrator, Freehand, and JPG formats).
It is relatively easy to create (or modify) such design guides with whatever mapping software you are using (even customized for specific projects), and then print or view them on the final media upon which your map will appear. For example, if you plan to print your map on a photo quality ink jet printer, print your design guide on that printer, and use the printed version to guide your graphic choices (not your computer monitor, where the colors will look significantly different).
The files below were created on my Mac and I cannot guarantee the Illustrator and Freehand copies will work with your computer, operating system, or software. You can at least use the JPG version as a model for creating your own guide in your software (with your choices of colors, fonts, symbols, etc).
Download:
Making Maps: Graphic Design Guide: Adobe Illustrator CS2 version
Making Maps: Graphic Design Guide: Freehand MX version
Making Maps: Graphic Design Guide: JPG version
Making Maps: DIY Cartography 
I like it:)
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