Many thanks for all the responses and suggestions.
Chris: I will look into Fotosketcher. I used to use Sketchup a lot, but I found that even with its myriad of output styles, it is tricky to escape that 'sketchup' aesthetic.
George: Those MLK Library visuals are very interesting, and quite refreshingly different.
Clive: You're absolutely right of course, being a visual artist involves far more than simply producing photo-real renderings.
Simon: Thanks - these links are great starting points!
Yama: Your project is great - thanks a lot for the inspiration!
Corey: Again, what you say is true. I am a fan of Luxigon - the images they produce are always more suggestive and evocative than definitive, which I think is the direction we should be heading in.
Thanks again!
D.