The DB as I'd envision it would be every keyboard ever known to any geekhack member. It would not be used to show off what we own but rather to document them. Same type of deal as current keyboard reference wiki but would allow easy cross-referencing by switch type, plug type, original computer it was shipped with, price range and so forth.
It would have a proper multiple table layout, not like some excel spreadsheet. Tables for manufacturers, connector types, every attribute of a keyboard. This allows for a maximum cross-referenceability...if that's a word.
Historical pricing reference would be a nice touch: known highest, known lowest, most recent and original would be a solid pricing guide. NIB could be excluded since NIB will generally (or should, at least) go as auction anyway.
This is something that requires thought and pre-planning. A proper database will have its full structure implemented in the beginning...I'd say that if less than a month of organized planning and thinking about structure and required fields went into it, it doesn't have sufficient pre-planning.
It would have a full-featured front end allowing lookup of all keyboards matching any particular attribute. Photos would be nice.
A technology similar to that app for Android that can do a search for something based on a provided photo rather than text would be awesome, but difficult as hell to implement I suspect. It'd need to compare a user provided photo against all photos of keyboards in the database then return records for matching units (would be useful for those no-name keyboards that don't even have FCC IDs)