A couple of characters have been on more than one cover, the usual suspects: Optimus, Megatron, Bumblebee, Starscream, Hot Rod, Ironhide. Prowl even appears on two covers in a row (in volume number). Honestly it could have been planned out better. Check out the gallery of the covers here:

https://tfwiki.net/wiki/Transformers...lection#Covers

I haven’t been able to go to my post office for a while, might have to make a dash soon.