I'm confused... which REH Solomon Kane stories did you read that were previously unpublished? Except for "Blades of the Brotherhood" (and a handful of fragments that were completed by other authors) they were all published during Howard's lifetime.
If you just didn't like the Solomon Kane stories... I can fully understand that. I'm just not quite following the "collecting dust in a drawer" or the "posthumously published" gist of your argument and how it pertains to these stories. The bulk of the "Kane canon" (if you will) was published between 1929 and 1932 in Weird Tales.