These are Zazzle stamps. The only personalized stamps I see in the back of the Specialized Scott catalog are for "Stamps.Com" stamps.
I created a sheet of Zazzle stamps and used them in conjunction with other stamps for the US Coast Guard issue last year. Here is an example:
I don't disagree that these stamps, on cover, may be of some interest some day, but I don't see Scott cataloging the Zazzle productions.