Is there any evidence that displaying a hero banner for mobile eCommerce results in more conversion / engagement that surfacing actual products in place of said banner? I have a hunch the latter will convert better, but would be curious to see any results either way. Lots of googling has led to nothing yet.
Not sure what your initial search query was, but here is the #1 result that I found in my search:
The key takeaway for this article is:
“Long despised by CROs everywhere, it looks like the rotating hero slider is finally going away. This year’s list sees only 2 sites still rotating the hero banner, down from 7 last year.”
The example shown is Nike, who no longer uses a hero image on mobile and gets right to work immediately exposing products to the user.
It's worth taking a look at the rest of Inflow’s Best In Class Ecommerce Mobile Report to see what other "major players" are doing. (Hint: Most of them have dropped the hero image completely.)
Additionally, I'd suggest you revisit your Google search and try different keywords (my search was simply "ecommerce mobile site are hero images worth it" -- there are likely better searches that would yield even more info).
To be fair, there are other articles I found with further points to be made:
Do Hero Images Prompt Ecommerce Conversions? - The key takeaway here is that if you do use hero images on mobile, make sure they scale properly. Nothing worse than an ugly hero image that is too small to do anything with (Fitts's Law). You should be using a product-based hero image (instead of a contextual hero image) to expose products with a call to action. Just make sure the CTA is usable!
Mobile Ready Hero Image guidelines for e-commerce - This site claims that hero images improve conversions on mobile and offers guidelines for usage. Here is the research they are using to back up this claim.
And so on. There seem to be differing views on the matter... so I'd suggest taking a long, hard look at implementing a split test to see which works best for your users.
Edit: Whoops, just noticed how old this question was (2 yrs!). Maybe that's why this information wasn't available at the time. :-) Hopefully my answer helps other Googlers, then!
A hero image is simply a visual design trend. Like any visual design, how it's implemented, and the context its implemented in is going to be the primary factors.
In other words, it's really impossible to say, generically that a hero image increases or decreases conversion or engagement. It's all going to come down to the particulars of your company's implementation in the context of your product and customers.