Try these two:
For an old-time view from across the street,
http://www.readingrailroad.org (click on Photo Galleries, then Stations). RCT&HS may also have a back issue of the Bee Line available that published some more photos and technical drawings (I think it was from 1984, to coincide with the Terminal closing.
For views inside the waiting room, concourse and trainshed from the early 1980's, go to
http://fp.users.fast.net/jprock/Default.htm
If you're anywhere close to Philly, you can visit live, since Reading Terminal is the centerpiece of the Pennsylvania Convention Center. The interior has been substantially modified including the construction of a two-story building in the north end of the train shed, but the exterior is pretty much as it was, except it's much cleaner and now sports a Hard Rock Cafe' guitar under the P&R President's corner office window.
Also worth checking out is
http://www.readingviaduct.org.
Andrew