The tail of the stamp has "Chamudi" (the HMO's current mascot) on it. "Chamudi" is a comic-strip character created by Daniela London-Dekel and published for a long time by Ha'aretz weekly supplement. It moved to "Yedioth Achronot" newspaper about three years ago. It is also the HMO service's mascot for roughly five years now.
Here is a link to a good strip published at Ha'aretz a while back: