Weeeelll, there are varying degrees of synergy. As above, the best to go with scorched earth is conflagrate. But there are some things that also go well-but-not-great with it.
-Undead take reduced damage from scorched earth, and are weak against aquatic pets where your moth is strong, so that ghostly skull is a good fit and difficult to replace. If keeping an undead in there is an option, but you're tired of the skull, I'd suggest camping for an HH Scourged Whelpling or Restless Shadeling and using Plagued Blood, which can help your team survive longer, and it's just annoying enough to sometimes cause a pet swap, giving you a free turn.
-A pet with Wild Magic, ala the Corefire Imp, will make those Scorched Earth ticks hit harder, as well as the imp's own immolation and the scorchling's Flame Breath.
-Both sides get to use that scorched earth, so to cover a weakness to other conflag teams you may want something with an aquatic attack. A snail will take less damage from an opponent's elemental attacks, but its dive is way too telegraphed to count on it being very effective, imo. A spirit crab might be good, because it can either shell or simply take less damage from the scorched earth and surge vs elementals, but I'd lean towards a P/P Emperor Crab. It can shell the scorched earth damage, surge enemy elementals, and bring either a self heal or a team heal to the game.
Hope those give you some fun options to consider. Good luck!