Answer: Over the years collectors have made it clear that they prefer their first day covers with cachets, the informative illustration usually on the left hand side of the envelope. In recent years overall cachets covering all or most of the envelope have become popular. These include the artist "hand-painted" covers which usually command a premium over such mass-produced fare as that marketed by Artcraft, Artmaster, Fleetwood and other popular brands.
As supply and demand dictates price the limited artist covers, almost without exception, sell for more than their numerous commercial counterparts. In any event, blank first day covers with only stamp and cancel are virtually worthless in today's stamp collecting marketplace. In general, only stamps first day canceled pre-1920s -- before the cacheted cover came into vogue -- are deemed collectible without a cachet.
But take heart! If you are of an artistic bent you might consider putting your own stamp-related artwork on a cover. Thanks to the ease of printing with computers we are in the age of the "add-on cachet." If you can draw, print and paint your first day cover collection might not come up blank after all!