When designing a mural one of the great pleasures is to consider the space as an oppurtunity for an experience rather than just a decorative way to symbolize an expression.
What I mean by that is that if we consider the room or exterior space as a place that can be approached from a specific "other" place (as through a doorway or around a corner) there is a particular point that is first revealed and then the perspective of the space is fully revealed as one experiences the space more directly. We often forget that part of an experience happens before our recognition of "the experience"... and so when dealing with an installation or the environmental scenery of a space, to get the greatest effect of the mural, we must examine the environmental psychology of the "optical conditions of the approach" and exploit the oppurtunity of extended impact to the viewer with an appropriate continuity of the intended experience.
There are several devices that can be employed. Observing the already present fluctuations in lighting can create natural courses of composition that can really play up the legibility of the mural image, highlighting areas and diminishing attention in others... or even directing new lighting installations to greater control over the experience. Obscured viewpoints can create a sense of wanting to look at parts that may be hidden, so as to discover an "easter egg" concept that may be the lynchpin to understanding the greater message of the mural. In this case, the viewer would be required to move and actually interact with the artwork, so that the spatial relationship is becoming more personal and complex at the same time.
And so, here, I'd like to take a moment and set out a working definition of what I feel art should be... in one word, an experience... and there are three experiences of the artwork... the experience of the work itself (eg. where it is shown, it's preservation, etc.), the experience of the viewer (what they bring to the experience and what they walk away with), and the experience of the artist (which should take all 3 experiences into consideration). I feel that the true integrity of an artwork is in its intention, otherwise it is merely an experiment. When the execution of the artwork matches the intention with a greater sense of appropriateness then we can judge the artwork to have a greater amount of quality experience for the viewer (provided the viewer has the appropriate level of knowledge required to understand the content- which is what the artist must consider when creating the experience and appropriately anticipate the legacy of the work to enable continous opportunites for a quality experience.) To continue discussing this would be to open a Pandora's box of theory and discourse of what those specifically could or should be, but I simply would like to defer back to the position of what the intention is in that space and how to enhance that intention with the use of Art --and let this awareness guide certain questions and certain answers to the mural designing process. In my experience, putting hard questions into beginning stages of the design process have made the follow through of the design easier and more rewarding. Therefore, let us look at the beginning of the design process as the point of greatest freedom and potentiality and moving forward is a process of editing and specifying each aspect towards the intention with a high-quality experience as the result.