Usually the aesthetics of the game (models and maps) are stored in a collection of files called the cache. People mainly use 317 revision because of the sheer amount of resources and information available for this client and its protocol.
Now when people have 317s loading higher revision data it's usually a matter of taking a cache from a later revision (377, 474, 600+ etc) and extracting or "dumping" the model files and map files from the cache and then importing and replacing their old files with the new. Now there's a catch here... Depending on how the newer revision's file formats are there may be a need to do some actual editing to the client's source. Such as adjusting the parts of the code that read the model formats and calculations for how things are rendered (model headers?) I really don't know too much about that though, I'm sure someone else can chime in.
For spell books that can also be found in the caches but they are listed as sprites and not models, and you'll need to dump the interface data or recreate them (pretty easy as it seems just familiarize yourself with RSInterface.java in your client and look at the Tutorials/snippets section to get an idea on what people are doing.)
I'm not a guru; I wasn't fortunate enough to be active during the glory days when alot of the people who know as much as they do about the client, gained their knowledge and it was shared and studied openly but I have a laymans' knowledge when it come to the general idea of the much simpler things.
Regards.




