John,
You might try thinking outside your original box. While Numbers might give you a decent fix, you also might try a different program designed for just your project. I searched in the Apple Downloads for 'Inventory' and found a program called 'Home Inventory' (too easy, right?). Check it out here:
http://binaryformations.com/
Some features:
--Nice user interface
--Categorization by type, location, etc.
--Nearly unlimited photos can be associated with your items
--Ability to create detailed reports for your records
--Shareware: only $22 (try before you buy and record 25 items with trial)
I realize Numbers is a great program for many tasks, but I think that from the looks of it, this program will do a better job at your specific task.
If you really wanted to pursue the Numbers solution, you could go about your inventory using a Numbers table and then list the location of each photo (/Photos/Home Inventory/12345.jpg) in a separate column. That way, you have all the functionality of a sortable, searchable table with the convenience of the photos somewhere else (non-bogged-down file as you desire). Perhaps you could print your photos in a thumbnail view where the names are listed; combine the smaller pictures with your table and you now have an all-in-one record of your possessions. Backup both for security and you should be good to go. If you ever need an item photo, just find the corresponding photo name for the item on your chart and then easily find it in your Home Inventory photo folder.
Just my thoughts. Hope they help!
-John