We are currently in the process of creating another flash tutorial on how to incorporate your own artwork in Illustrator Symbol Libraries, but in the meantime here are the steps.
1. Create a new file and save it with the filename that you would like for the name of the symbol library palette
2. Click Window | Symbols to make sure the main symbol palette is showing
3. Click on the small right facing arrow at the top right of the symbol palette and select ?Select All Unused? and then click the trashcan at the bottom of the palette. The palette should now be empty and ready to add your symbols
4. Open up your files with the artwork that you want to put into the library
5. To ensure font compatibility be sure to convert any text that may be in the artwork into outlines by right clicking on it and selecting ?Create Outlines?
6. Copy the artwork into the file that you setup with the pallet name in Step 1
7. Resize the object as desired
8. Drag the object into the main symbol palette
9. Double click on the new symbol to give it a new name
10. Delete the artwork from the main part of the page
11. Drag the symbol from the symbol palette onto the page and then delete it from the page (this is simply a checking step to verify the symbol works)
12. Repeat steps 4 to 10 until the symbol palette contains all the symbols you require
13. Make sure the main part of the page contains no artwork
14. Make sure the symbol palette only contains the symbols you want included in the library
15. Save the file
16. Copy the file to your Illustrator / Presets / Symbols folder which is usually: C:\Program Files\Adobe\Illustrator (10 or CS)\Presets\Symbols
17. Close Illustrator and restart
18. Your new symbol library can now be accessed via Window | Symbol Libraries
19. Repeat 1 to 17 to create multiple new libraries
20. To add new symbols to the library at a later date, simply open the file that you copied to the Illustrator / Presets / Symbols folder and repeat from step 4
Please let me know if you have any problems or any other questions relating to symbol libraries,
Adrian