There really isn’t, not in the way you mean. Anything that any of those artists did for Marvel that was of a professional quality was printed.

There might be other pieces that they did for one thing or another–commissions or pages/covers that were rejected for some reason, etc. But that’s very catch-as-catch-can, and we wouldn’t automatically have the rights to those images.

Plus, it feels to me a little bit shady to do a whole month’s worth of variants trading on the memory of a deceased artist, who’d receive no payment from them, and would have given no consent to their use. On occasion there’s a piece that we’ll negotiate with the next of kin to use in some manner, but there really isn’t the sorts of numbers of unused pieces to make a whole program out of it.