If you're working with original art, always take the most conservative approach. Right now, that means no pressure-sensitive adhesives -- there are none that have been demonstrated to be conservationally safe and reversible over time. The standard is still rag paper and wheat-starch paste. Stamp hinges are probably the best low-moisture method for affixing paper labels to works on paper (although simply using a graphite pencil either in the undermatte area or on the back would probably be easier).

If you are affixing the labels to canvas stretchers or mounting boards well clear of the actual artwork, then you can get away with just about anything.

If you are going to build a comprehensive database, then all of the information you're talking about is going to be valuable over time -- particularly the list of materials used. It will make a conservator's job a lot easier if the work ever needs to be cleaned or restored. If you can include a list of pigments, that's great -- it can help in reducing chemical damage. More important, though, is the varnish (on oils and often on acrylics) if you know what was used.

Added: The best reference to consult is probably still Ralph Mayers' The Artist's Handbook of Materials and Techniques (always the latest edition, since new materials are assessed as they become available). Yes, he's opinionated and conservative, but that's mostly in reaction to the short-lived disposable (but not inexpensive) art that was being produced when he wrote the book in the first place.