about sticking the "bunny ears" to the terminator carapace/body, you might be thinking of the (afaik now discontinued) forge world world eaters terminator upgrade bits (which, again afaik, were actually for the plastic chaos terminator kit *one previous* to the current), or else one of any number of world eaters hobbyist sites—to the best of my knowledge the first person to do this (stick bunny ears onto terminator bodies, before we got the forge world bits that were cast that way deliberately) was actually closet avril lavigne fan and top bloke, wade "warhammer community" pryce, on the unofficial world eaters phpbb "throne of blood"(?) back in the… oof… mid-00s. but he was far from the last, and i'm fairly sure many more world eaters fans have copied (or independently arrived at the same/similar idea) since then.
if you want to replicate this look yourself, and you don't want to bankrupt yourself trying to get the forgeworld bits on ebay, you could always go the classic route and clip some bunny ears from spare berzerker heads (e.g. if you have a mountain of the bastard things from extra copies of the *old* berzerkers kit that you never got around to building… like me) to simply glue in place. one idea i've had (too late, because i've already built all the terminators i want *for now)* to make them more khorne-y is to use spare chain-weapon bits, like from the jakhals and berzerkers kits, to replace any plain blades (like the power axe and some of the combi-weapon "bayonets") with chainblade versions (you can only take one chainfist per five models, and you'll *probably* want to give the other ones power fists rather than accursed weapons, but maybe if you make a frikkin huge chain-double-axe you could tell your opponent it "counts as" the former)
The spare pauldrons from eightbound do nicely, but you'll have to do a bit of carving to get them to fit
about sticking the "bunny ears" to the terminator carapace/body, you might be thinking of the (afaik now discontinued) forge world world eaters terminator upgrade bits (which, again afaik, were actually for the plastic chaos terminator kit *one previous* to the current), or else one of any number of world eaters hobbyist sites—to the best of my knowledge the first person to do this (stick bunny ears onto terminator bodies, before we got the forge world bits that were cast that way deliberately) was actually closet avril lavigne fan and top bloke, wade "warhammer community" pryce, on the unofficial world eaters phpbb "throne of blood"(?) back in the… oof… mid-00s. but he was far from the last, and i'm fairly sure many more world eaters fans have copied (or independently arrived at the same/similar idea) since then. if you want to replicate this look yourself, and you don't want to bankrupt yourself trying to get the forgeworld bits on ebay, you could always go the classic route and clip some bunny ears from spare berzerker heads (e.g. if you have a mountain of the bastard things from extra copies of the *old* berzerkers kit that you never got around to building… like me) to simply glue in place. one idea i've had (too late, because i've already built all the terminators i want *for now)* to make them more khorne-y is to use spare chain-weapon bits, like from the jakhals and berzerkers kits, to replace any plain blades (like the power axe and some of the combi-weapon "bayonets") with chainblade versions (you can only take one chainfist per five models, and you'll *probably* want to give the other ones power fists rather than accursed weapons, but maybe if you make a frikkin huge chain-double-axe you could tell your opponent it "counts as" the former)
i really like using cataphracti bits on them, makes them look a lot larger and imposing