Yep, they originally planned to have rewards for ranking high on the leaderboard, but it got scrapped. It was probably going to be those frames you mentioned. Their description certainly made it look like those were the planned rewards.
I was number 9 or 10 in solo, and my group was number 3 in trio, and we got nothing.
It was revealed in the 2.0.14.1 patch notes that rewards were going to be given out. The patch notes have since been altered to no longer mention rewards. You can read more about it in the following link, and see a reply from Hedge saying it was cancelled. Vermintide 2 - Patch 2.0.14.1