Domi,
My experience with the Shuttle has been strictly from a Mission Control standpoint. Strangely, while I've supported every mission the shuttle has flown,
I've never been "up close and personal" with the orbiter. I just now wandered down the hall to the control room and looked at our photos of STS-30 which was
the Magellan mission. The photos of the payload bay with Magellan perched on the IUS (inertial upper stage) are useless from a modeller's point of view.
As for the tiles, they are fitted very, very closely together. There can be NO GAPS
between them if they are to protect the orbiter. Personally, I'd ignore the tiles
as I think it would be too much work to represent them but, that's me. If I were to
attempt to represent them, I think I'd paint the area a dark grayish black and use
a 0.1mm mechanical drafting pencil to draw on the lines and then seal them with
a clear coat. As for detailing the payload bay, a company called "Real Space Models" has a 1/72 payload bay kit as well as a kit for the proper engines.
The URL to their site is: http://www.realspacemodels.com/html/catalog.html
I believe this company works with Launch Complex Models but, I'm not completely sure of that. I know this isn't much but, I hope it helps you out.
BTW---I supported STS-1 from a former British colony---No, not the US of A---
The Seychelles Islands where I was brutally forced to live for six years.
Cheers,
Ray