It may be useful to prepare a bunch of fake or real covers to put the tentative logos onto, to see how they work in practice.

That is a good idea! If anyone seeing this comment is a publisher who has some cover images that you are OK with using, I will collect a couple and add to the main page w/ instructions to use for examples. 

I see that your submission has a few https://itch.io/jam/ttrpg-system-agnostic-badge/rate/1473669 - would you mind sharing those for use by others?

Thanks Lux! Cheers