That’s something that companies that make candy, shampoo, movies, fast food, cars, and so on, have all figured out. The comics companies (outside of the Big Two, the Fantagraphics/D&Q types, 2000AD, etc.) don’t really even do a lot of Branding 101 stuff, they haven’t asked who their customers are and how they want their product to make them feel, they haven’t created a recognizable look or a company-wide “voice” that stands out from their competitors. I doubt they have anyone on staff who does this stuff.
I don’t think the “every book is an island” approach that Image has adopted is a great one. There needs to be some kind of unifying quality control, and support for all titles across the line with the big titles a tide that lifts all ships. In a great and well-marketed line you need to feel like you’re not just reading some comics, but that you’re in on something cool, a part of something special. Think of peak era Vertigo or Windstorm. Y The Last Man and 100 Bullets owe so much to the fact that people loved Preacher and Transmet, which owes to the fact that people loved Shade and Sandman, and so on. If you love Lazarus and Jupiter’s Legacy, why buy another Image book? Who knows what you’re getting.
I am sure “indie” comics lines of the 90s thought about it like the indie record labels of the 80s, where labels like SST or 4AD or whatever almost had a whole aesthetic and way of life attached to them. If you liked Dead Can Dance, you would probably like the Cocteau Twins, and so on. If you’re going to run a boutique comics line, that’s how you have to think about it. I’m 100% certain Vertigo did back in the day.
(And Valiant is pretty good at this, but they have other concerns, namely good entry points)