The 25th Rune rule is a little strict, I think.
Granted, the original volva seers didn't use a blank rune, but that doesn't mean you can't use it if you want to.
Personally, I do have a 25th with one of my sets, but as a rune added myself, not as a blank. ( strangely enough, the symbol I use on that rune, which has been my little icon for years, and was totally original in concept, turned up reversed in a runic font i found yesterday!...weird...!)
I have never used cards as a method of runeworking. I think that if you are, then think of them of cards, as i do not think they will carry the same depth of emotion as stones or staves. However, i might be wrong.
On the other hand, they will introduced the concepts ok, and the use of pictures might help you *comprehend* the meanings of each symbol easier than texts, assuming the artist was well informed.
Keep me posted on this, I'd like to know how well they work.!
Oh, and Celtic Runes could be a mix up with the Ogam oracle, which is just as interesting, but very different in interpretation...its not fake per se, just not the same....