When building an rpm package from a tar.gz file with a "Logo:" line in the spec file rpm doesn't find the specified logo file in the tar.gz file even though it's there, thus rpm packages cannot be built with rpm -tb file.tar.gz.
You will need to rebuild using "rpm -bb specfile" and putting foo.logo in the SOURCES directory (usually /usr/src/redhat/SOURCES). Rpm has no way of identifying that foo.logo in the tar ball has any relation to foo.logo mentioned as "Logo: foo.logo".