Indexes are just to speed up queries. Ideally, you need to index those columns that:
a) are queried often (each primary key fields)
-and-
b) have a low degree of similarity (ie most values are unique)
Indexing binary content is a waste of time, as far as I can tell, since you can't place binary criteria in your SQL statements...
Cheers
Ken
www.adOpenStatic.com