Visualization is the term I use to describeillustrations, collages, sketches or images used to communicate game design (note: not narrative or visual style), and also includes any templates or guidelines used help create them.
As a game design tool, visualization is used to create tangible design (something others can evaluate), which allows the designer to communicate more intuitively or providing a visual reference to design ideas . These techniques are derived from other creative fields (i.e. animation, film, new media, graphic design, etc.) and have been adapted to game design. Visualization is usually used to support the design and tuning phases of game design process. Visualization can be used as an addition to other game design tools (i.e. game design documentation), or offer an alternative tool for designers that are more visually oriented. Several visualization methods have been criticized as being techniques derived from linear and static media, and are thought to be unsuitable for describing game mechanics and play mechanics. A typical pitfall in using this tool is emphasis on narrative and visual style, while failing to describe the essential game design elements.
(1) Visual vs. Textual
It is a question of knowing who will be the audience (e.g. the development team) of the text or visuals. Some audiences will demand in-depth description that visuals do not typically achieve, while other audiences will praise the use of visuals as being simple and to the point. A good combination between text and visualization is probably the best way of solving the issue.
(2) Visually Oriented Game Designers
Using visualization techniques to communicate game design can be an alternative for game designers that are more visually oriented and allergic to writing. Visualization can communicate intuitively and implicitly, where written language cannot. To accomplish this the designer needs to be able separate game design and game art issues.
(3) Mood Board-Collage
The mood board-collage is typically used for determining the game art direction. Used for game design it can be used as way to provide an impression of the game play-experience.
(4) Diagram Mock-up
The diagram mock-up is usually a kind of screen shot combined with call-outs and other diagram elements to describe how things move and interact during game-play.
The storyboard which is more often associated with explaining narrative, can also be used to explain the game's design by providing a walk-through of the game mechanics.
Books with information about visualization