I recently came across a fantastic collection of behind the scenes photos of the original USS Excelsior miniature. According to a couple of forums where they've also been shared previously, these originate from Star Trek visual effects artist and miniature maker Bill George.
The pictures show the miniature, prior to the Generations refit, in great detail, and appear to have been taken through the course of using the model on TNG and DS9, with several of alternate ship names used when the Excelsior class was seen in those later series shown here. Continue below to check them out:
Here are some of the other Excelsior class ships, all using the same miniature of course; the USS Hood, USS Melbourne, and USS Repulse:
There's a huge series of photos recording all the detailing of the model. A great reference for any model makers:
And a whole bunch of photos showing work being done on the model, giving a unique look at how it's built:
There are a few more (either similar or slightly fuzzy) shots in the original Imgur gallery where these were first shared. And if you're interested in the history of the model, Ex Astris Scientia and Memory Alpha both have great detailed articles about it.
If you enjoy seeing the original models, check out some of my previous coverage for a similar look at the USS Enterprise-E, USS Pasteur, the Klingon K't'inga class, the ships of the Battle of Wolf 359, and USS Curry, or have a dig around my behind the scenes tag for a whole lot more.